His outfit sucks for one thing ;) But here are my grievances with him. Gameplay-wise he has access to all our his styles, but they feel gimped from their levels in dmc3 and the enemies all feel like they're designed mostly around Nero, so Dante isn't as much fun at a causal level, and that's before you talk about his actual levels.
DMC4 is also the first game with an actual story that really treats Dante as being invincible which is a negative imo. Also, some fans thought immature DMC3 Dante would turn into DMC1 Dante cool, honorable, chill, but full of swagger Dante. Instead Dante became this unstoppable meme machine, which can be fun, but isn't as cool as Honorable trash talker Dante. After dmc1 Dante was powerful, but wasn't invincible. He only beat mundus because he used Sparda and then got a temporary power boost from Trish that still didn't kill mundus. DMC2 was DMC2 and Dante seemed OP, but you could easily clear that up by saying the 2 demons were weaker than mundus or ignoring it like they did for years. But in dmc4 Dante is portrayed as invincible and treated everything like a joke. Now the team acts like Dante is too strong to be the MC of the series. I obviously disagree with that lol
DMC5 Dante came off as an ass cause all of a sudden he was super about killing his brother and was more rude with Nero and Patty, which goes against his more playful and chill personality from the previous games. He needed a few cutscenes to establish that he cared about all the victims, his friends, and show why he was so determined to kill Vergil. If you follow the series you can make up reasons why, but it should have been shown. We needed to see more of Dante's inner turmoil then we received.