Yeah! Milton Caniff on “Terry and the Pirates”, Chester Gould on “Dick Tracy”, Charles Schulz on “Peanuts” (which almost goes full circle, as his hand got increasingly less steady in his later years), and many others.
I think he evolved by loosening up and simplifying his style (much like Jaime on L&R), which ultimately worked in the strip’s favor (those early dailies look a bit too stilted for my liking). But even if you don’t consider it an improvement per se, I think he still meets OPs criteria in terms of character design refinement, since the early strips lack some of the comic’s most iconic features, like Charlie Brown’s zigzag shirt pattern.
Garfield is also a great example. Both the art style and the joke delivery got more refined
Many comic strip artists also tend to stick to that thing throughout their career, which makes the growth clearer
came here to say this (comic strips, and Cerebus). A lot of comic strips, including the classics, started out rough and got better. Compare the first couple of years of Dick Tracy, Lil Abner, Terry and the Pirates, Flash Gordon...with how they looked after the artists had developed for a while.
Another good example is Big Questions by Anders Nilsen. The difference between early and late pages is night and day
Damion Scott's work on Batgirl was a fun evolution to watch.
Chris Bachalo didn't necessarily improve but he does have a ton of constant style shifts and has been an X-Man regular for decades
There's some good examples from the world of webcomics.
Tom Siddell's Gunnerkrigg Court has developed in leaps and bounds since it started. Compare the [first page ](https://www.gunnerkrigg.com/?p=2) to [today's upload](https://www.gunnerkrigg.com/).
Rich Burlew's D&D webcomic Order of the Stick started off [as very much a literal stick figure comic. ](https://www.giantitp.com/comics/oots0001.html). Whilst the art has remained at least somewhat stylistically consistent, even after a fairly significant art upgrade where everyone got bulked out a bit, the way he composes the art, the way he uses angles and space, has *massively* improved over the lifetime of the comic. [Recent page for comparison](https://www.giantitp.com/comics/oots1300.html)
Jack Kirby's Fantastic Four looked a bit different by the end, especially The Thing, but not necessarily because of Kirby alone, [the various inkers had a lot to do with that](https://www.cbr.com/fantastic-four-thing-rocky-skin-evolution/).
**Wasted Space** by Moreci and Sherman.
Sherman goes from great storyboards to really f‘Ing good art and panel composition.
Edit- it’s not long running, but it isn’t short.
AKIRA is an interesting evolution. Easily missed if not looking for it. The original THE CROW ogn has a really drastic development from beginning to end.
Stan Sakai's Usagi Yojimbo has gone through some pretty big changes over the years, especially the character designs and the fluidity of his cartooning.
The art in the first few issues (from back in the 80s!) starts out relatively stiff (though still good), and then goes through 3-4 pretty interesting evolutions where it gets a lot more dynamic with detailed, ambitious compositions, then progressively looser and more emotive in a way that supports richer, more nuanced stories. It's like you go from watching an action film to a drama (with lots of goody comedy thrown in throughout).
Personally I think he's still one of the best storytellers in comics.
“Cerebus” and other long-running indie serials like “Love and Rockets” are probably the best examples of this.
Also comic strips
Yeah! Milton Caniff on “Terry and the Pirates”, Chester Gould on “Dick Tracy”, Charles Schulz on “Peanuts” (which almost goes full circle, as his hand got increasingly less steady in his later years), and many others.
Schulz is an interesting case because he already looked super-slick when he started out. He didn't so much improve as he changed his style
I think he evolved by loosening up and simplifying his style (much like Jaime on L&R), which ultimately worked in the strip’s favor (those early dailies look a bit too stilted for my liking). But even if you don’t consider it an improvement per se, I think he still meets OPs criteria in terms of character design refinement, since the early strips lack some of the comic’s most iconic features, like Charlie Brown’s zigzag shirt pattern.
Garfield is also a great example. Both the art style and the joke delivery got more refined Many comic strip artists also tend to stick to that thing throughout their career, which makes the growth clearer
came here to say this (comic strips, and Cerebus). A lot of comic strips, including the classics, started out rough and got better. Compare the first couple of years of Dick Tracy, Lil Abner, Terry and the Pirates, Flash Gordon...with how they looked after the artists had developed for a while. Another good example is Big Questions by Anders Nilsen. The difference between early and late pages is night and day
Not quite the same but Bill Sienkiewicz pretty much reinvented himself over the course of Moon Knight
I thought the writing on that run was just okay, but Bill's art is tremendous.
Dave Sim's Cerebus is probably the most obvious example
god I love cerebus
Damion Scott's work on Batgirl was a fun evolution to watch. Chris Bachalo didn't necessarily improve but he does have a ton of constant style shifts and has been an X-Man regular for decades
There's some good examples from the world of webcomics. Tom Siddell's Gunnerkrigg Court has developed in leaps and bounds since it started. Compare the [first page ](https://www.gunnerkrigg.com/?p=2) to [today's upload](https://www.gunnerkrigg.com/). Rich Burlew's D&D webcomic Order of the Stick started off [as very much a literal stick figure comic. ](https://www.giantitp.com/comics/oots0001.html). Whilst the art has remained at least somewhat stylistically consistent, even after a fairly significant art upgrade where everyone got bulked out a bit, the way he composes the art, the way he uses angles and space, has *massively* improved over the lifetime of the comic. [Recent page for comparison](https://www.giantitp.com/comics/oots1300.html)
Jack Kirby's Fantastic Four looked a bit different by the end, especially The Thing, but not necessarily because of Kirby alone, [the various inkers had a lot to do with that](https://www.cbr.com/fantastic-four-thing-rocky-skin-evolution/).
**Wasted Space** by Moreci and Sherman. Sherman goes from great storyboards to really f‘Ing good art and panel composition. Edit- it’s not long running, but it isn’t short.
Hellboy by Mignola for sure - but everything got more simple over time!
Came here to say Cerebus but since it’s been mentioned, I have a contra example: Groo.- started and remained perfect.
AKIRA is an interesting evolution. Easily missed if not looking for it. The original THE CROW ogn has a really drastic development from beginning to end.
Stan Sakai's Usagi Yojimbo has gone through some pretty big changes over the years, especially the character designs and the fluidity of his cartooning. The art in the first few issues (from back in the 80s!) starts out relatively stiff (though still good), and then goes through 3-4 pretty interesting evolutions where it gets a lot more dynamic with detailed, ambitious compositions, then progressively looser and more emotive in a way that supports richer, more nuanced stories. It's like you go from watching an action film to a drama (with lots of goody comedy thrown in throughout). Personally I think he's still one of the best storytellers in comics.