I absolutely love Attack on Titan and it's one of the best anime's I have ever seen. Even the clown show ending from the manga has been fixed to an great extent in the anime. The anime has so many excellent moments which are some of the best written scenes in anime.
The fanbase is insufferable though. It's either full of "Eren is literally me" mfs or glazers with no sense of reality and I'm pissed at liking the same thing as them.
When did Armin do this? From what I remember, he was always against violence. Even when he nuked the Navy, he was clearly distraught from that.
Assuming you're talking about Eren after the rumbling started. Because during the duration of season 4, he was genocidal(wanted to start the rumbling) yet had great character development and moments when I sympathized with him. I didn't agree with him but seeing him evolve into a villain because of his never ending trauma was genuinely great to watch.