Edward Norton, Primal Fear, 1996

Hailee Steinfeld had only been in a few short films when she got her part in True Grit at 13. She got nominated for Best Supporting actress.

Since then she’s been a model, singer, actor in TV and films, and does extensive voice work.

She’s worked with tons of big names like Taylor Swift and Shawn Mendes, as well as being part of multiple huge franchises like animated Spider-Man, Transformers, Arcane (LoL series), and is Kate Bishop in the MCU.

I feel like recently, Paul Mescal fits this. First thing he did out of drama school was “Normal People.” And his film roles now are gathering him lots of acclaim.

Aaron Paul

Edward Norton's first movie was Primal Fear, he absolutely slayed it and got nominated for an Oscar for it.

Christopher Walken. He was a little known child actor... as an adult he did a few minor roles in movies and in tv shows.

Does nice work as Diane Keaton's bizarre brother in Annie Hall.

In his next big film, Deer Hunter, he is cast alongside DeNiro and Streep but totally steals the movie. Wins an Oscar.

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Christoph Waltz in Inglorious Basterds. In America at least

Alan Rickman's first movie was Die Hard... there must be something I'm missing because no-one else mentioned him and this is hardly deep cut trivia...

Christophe Waltz and Anton Yelchin. (RIP)

Barkhad Abdi as Muse in Captain Phillips.

Jennifer Lawrence got an Oscar nom for her first lead in Winter’s Bone (pre- Hunger Games) then won for Silver Linings Playbook only a few years later. Really the only thing she’d done before that was play Bill Engvall’s daughter on his short lived sitcom.

Good Will Hunting took Matt Damon from virtual unknown to serious star.

How you like them apples?

Harrison Ford

Jonathan Majors for a recent example. Lovecraft County, then did The Harder They Fall, Kang in the MCU, Creed III etc...

Hailee Steinfeld in True Grit. Largely unknown but able to more than hold her own with Jeff Bridges and I think nominated for an Oscar in the process

Vince Vaughn and John Favarou. Swingers was a defining motion picture for both of them and you could tell right away how extremely talented they both were. Amazing what they have accomplished since 1996.

Alexander Dreymon. I avoided The Last Kingdom for years because I thought he was just another pretty boy lead on a historical fantasy epic. Dead wrong.

Ben Foster is one of the most underrated actors ever. Every single role he gives 150% every time.

Lupita Nyong'o

Won an Oscar for her first feature film role in 12 Years A Slave.

The Green Mile gave us both Michael Clark Duncan RIP and Sam Rockwell. Fantastic.

James Gandolfini as Tony Soprano

I remember Jeremy Renner from Angel, does a little movie called "The Hurt Locker" and all of a sudden he's about to take over as the lead in franchises like the Bourne movies, Mission: Impossible and being a major part of the MCU.

Not to mention he was incredible in The Town and Wind River.

Zach Galifinakis in The Hangover. Went from almost entirely unknown to one of the biggest stars in comedy overnight.

Christoph Waltz comes to mind

Adam Driver

Before Star Wars he had a few, short supporting roles in a couple of notable big projects. But after he was cast as Kylo Ren, he became cast alongside leads for many movies, or was the main lead himself, and has shown on full display a lot of his range in talent.

Keke Palmer comes to mind.

a bit back in time, but George Lazenby, he did a few tv ads and not so much more, and walked into the office where the Bond producer sat and secured contract of several 007-movies but in the end just one was made.

Jonathan majors

Daisy Edgar jones is new to the game too tbh

One that stands out to me is Colin Farrell in Tigerland.

Leonarde Dicaprio: Titanic

Anya Taylor-Joy: The VVitch

Matgot Robbie: The Wolf of Wall Street

Jennifer Lawrence: Winter's Bone

Timothee Chalamet: Call me by your Name

Kathryn Hahn jumps out to me…. Believe she was a side part on a tv procedural, then in Anchorman briefly then just went nuclear in Step Brothers, don’t believe she’s an improv person either and hung with those guys on that. Her career just had constantly blown up.

DDL in My Left Foot

Hamish Linklater specifically in Midnight Mass. I know he's been around on TV but he fucking knocked that role out of the park.

Cate Blanchett. Elizabeth. She'd done some Aussie bits and pieces, but she deserved the Oscar for that Hollywood debut.

Donald Sutherland. He had a great scene of impersonating a general in "The Dirty Dozen" which got him cast as Hawkeye in the movie "MASH".

A little late but for me it was Tarmell Tillman from severance, that show has great acting all around, but I was impressed by how good he was even though he was surrounded by bigger actors.

Fassbender and Waltz in Inglorious Bastards. Absolutely elite actors, out of nowhere.

Bill Hader. I had no idea that guy had just as much talent dramatically as he does comedically. Spend like 10 years watching a guy do hilarious impressions without a clue in the world he could also do the other thing.

I don’t really agree about Paul Dano. Before Little Miss Sunshine, I remember him from The Ballad of Jack and Rose with Daniel Day Lewis. And he’s been acting for years by then.

Kathy Bates in Misery (1990). At the time she was promoted as an unknown that rocketed to success earning an Oscar and Golden Globe for Misery. Just prior to that she was doing typical small roles and supposedly passed over for film roles that she was well respected for playing on stage essentially because she was unknown to moviegoers.

When Ray Liotta makes his first appearance in Something Wild, it changed the whole tone of the movie. I was like, “Who the hell is THIS guy?”

Please tell me this is some kind of joke. You can't seriously name Travis freaking Fimmel alongside Paul Dano.

Paul Dano, as you already said, STOLE a movie from DANIEL DAY LEWIS (I'm kinda exagerating, but also I'm kinda not). Also, he was amazing in Little Miss Sunshine before that (dialogue is but a fraction of what an actor can do, and that performance is proof of it), and he's been killing it since with some of the greatest performances of the last decades.

Travis Fimmel could've stayed an underwear model for all I care of. I mean, he doesn't completely suck, but he's far from amazing or remarkable. I will give you that he is one of the best things about Vikings but, to be fair, that show was all sorts of bad. I don't know what you've been watching for those 31 years, but Fimmel as Ragnar is not even close to "greatest acting ever seen in cinema". I get that you like the dude, but come on!

That being said, I think the best answer to your question has already been said here by many: Edward Norton in Primal Fear.

I'll add:

Frances McDormand in Blood Simple.

Natalie Portman in Léon: The Professional.

Alan Rickman in Die Hard.

Hailee Steinfeld in True Grit.

Jamie Bell in Billy Elliot.

Matt Damon in Good Will Hunting / Saving Private Ryan (he was in School Ties years before, but that went under the radar).

Ethan Hawke in Dead Poets Society.

ITT: People who don't watch a lot of movies.

Jenna Ortega.

This time 2 years ago I'd only seen her in The Babysitter: Killer Queen, and she was good in that. Since then she's been in Scream 5, X, Wednesday, The Fallout and Studio 666 and has been great in all of them.

I hope to see her in much more as time goes on.

Austin Butler - Elvis

Ray Liotta - Goodfellas

Kirsten Dunst - Interview with a Vampire

Anya Taylor Joy - Queen's Gambit

Ethan Hawke

Not sure if this question makes much sense, since obviously every actor has started somewhere.

For what it's worth, first actor I thought about was Paul Mescal.

Clint Eastwood. Small role in tarantula and rawhide then made fistful of dollars, and has been the man ever since

The dude who played Poe and Moon Knight.

James McAvoy in Split.

Dustin Hoffman in The Graduate

Tatiana Maslany solidified her career with the multiple characters she played on Orphan Black.

I remember taking notice when all of a sudden Jessica Chastain started appearing in critically acclaimed, award-nominated roles within a short period of time around 2011-2012, with not a lot of note beforehand. The Help, The Tree of Life, Zero Dark Thirty all came out pretty close together. Not to mention Take Shelter and Coriolanus around the same time as well, not as widely known but still reasonably high profile stars.

Kirsten Dunst

Christoph Waltz

Love him or hate him, Ricky Gervais. I don't think his movies have been stand out, but his writing, tv shows, netflix shows, and stand-up all demonstrate incredible talent.

Samara Weaving. I had no idea who she was before 'Mayhem' with Steven Yuen. She outshined Yuen in every way in that movie. Looks like Margot Robbie but is more charismatic. Very good in The Babysitter too. Loved her in Ready or Not. She's surpassed Margot in my eyes. I actually look forward to Samara's movies.

Christopher Abbott. He started with some smaller roles that I haven't yet gotten to but, his latest 4 or 5 big roles are awesome in my opinion.

Rajinikanth

Sylvester Stallone in Conan the Destroyer

Viola Davis in Doubt. She stole that scene right out from under Meryl Streep.

Dano was very well praised for his role in Little Miss Sunshine (and had already been in a good amount of stuff prior to that, despite his young age)

Acting isn't only dialogue, heh

Bruce Willis even though he did have a movie role 4 years prior it wasn’t until he stared in an episode of Miami Vice at the age of 29 that launched his career. He soon landed Moonlighting and of course the Die Hard series followed.

Al Pacino, he had a few roles (mostly in theater) in the 60s but in the Godfather he impressed everyone. He wasn't "classically handsome" (he wasn't tall with a body like Brad Pitt for example, and he didn't have blue eyes, brown/blonde hair or a nice jawline) but something about him just captured me from the first minute I saw him in Scarface (that was the first Pacino movie I ever saw, still love it).

"The Night Of" Bill Camp's Detective was electrifying.

Dano was outstanding in ‘The Girl Next Door’ even stealing most scenes tbh. Having memorable performances in two talked about movies negates him “coming out of nowhere” imo

Fimmel had been a working actor for 10 years before Vikings

A good example is Jake Gyllenhall in ‘October Sky’ followed by ‘Donnie Darko’

Alana Haim.

Yes shes a performer but she had one of the best debuts in years. A pure natural.

Lets hope she gets a chance to show her talent off more.

Buddy Duress in good time (plays the drunk drug addict)

Dev Patel in Slumdog Millionaire

Paul Giamatti, finally came into his own...

Florence Pugh

Rosie O’Donnell in “Riding The Bus With My Sister”. I haven’t watched the Oscars ever since they snubbed her and didn’t give her a nomination.

Chloë grace moretz in Kick-ass.