I don't think they spent a lot of time developing him, and the robot suit and mecha just felt completely out of sorts with his character.
I think the whole point of the story is what it takes to turn good men into monsters, which is what both Otto and Li end up being by the end of the game. It becomes less about a necessary evil and more fulfilling their revenge and satisfying their ego's no matter who they have to hurt in the process.I agree somewhat with Snoop Dogg with regards to the villains in the first game. Mr. Negative was very cool but a little underdeveloped, with the dynamic between the two personalities being largely unexplored. Doc Ock was great, but I wish we had more time with him in the third act. He barley has any time on screen after going bad. The other Sinister Six members were all cool when they were there, but they could have had a little more to do (especially Vulture, who is completely shafted). Shocker was fine. Kingpin was fine. I honestly think the biggest issue was that the whole "revenge against Osborn" plot was a little flimsy after a while. Like, I get that Martin and Otto were both justifiably angry with Norman, but by the end, they had caused so much damage to the city and killed so many innocent people that I had a hard time buying into the idea that they were supposed to be sympathetic. And maybe that was the point, that revenge turned them into worse monsters than the man they hated, but I feel like the game didn't do great job of establishing how they (more Otto than Li, perhaps) were justifying the action of releasing that toxin as necessary evil.
I thought they did enough to make Li interesting. Mr. Negative isn't so much a split-personality as just an expression of his more negative and violent emotions, and he can inject that into others.