It’s very faithful. The few changes that have happened are simply shifting around the order of events or adding extra dialogue/scenes that are always good. The only negative change I can think of is Amber knowing Mark was invincible for weeks. I have no idea why they even changed that since she was fine in the comics. There was a hilarious side plot where she thought Mark was a drug dealer, but she still figured it out before he directly told her.

I’m only halfway through the comics but so far the show is a really faithful adaptation but it’s not exactly the same. Certain events are shifted around and characters get a lot more development. But mostly it’s all very representative of what the comic did/was trying to do.

For example (no spoilers), Mark’s mission to mars doesn’t happen in the comics until after Omni-Man leaves earth. The plot with DA Sinclair and his Reanimen is spread out as a subplot across a lot of issues rather than one condensed story like in the season one episode. Most of the changes are stuff like that.

Aesthetics, tone, and most of the supporting characters are different to an extent. The plot itself is followed very faithfully but not in same order/pace necessarily.

Aside from changing the order of some events, overall it’s nearly entirely faithful so far. The changes and omissions that have been made have all been for the better in my opinion.

It’s pretty faithful in adapting moment to moment scenarios but the order of the moments have been shifted a lot. Like the Mars mission, Robot working with the Twins, Titan and Invincible facing Machine Head, and D.A. Sinclair >!all happened after Omniman left Earth!<.

Then there are some character changes like William already being out of the closest, Amber knowing Mark’s identity for way longer in the show and breaking up with him.