They say the best written villains are hard to even label as villains. Be it their motives, origins, etc, they make such a compelling character that it's hard to find fault with them, leading many to sympathize with or even go so far as to say they did nothing wrong.
Ikeuchi is NONE of that.
He's probably the most underwhelming, pathetic, disappointing villain I've ever seen. The girl he liked but didn't have the balls to approach didn't like him back, so the whole world has to be as miserable as he is for it. Right from his introduction, he's made out to be a pathetic victim of someone else's (lack of) feelings, which just continues to build until he thinks the whole world should burn for it.
Good riddance.
Orgin was when Shuichi secretly took Chihiro to find her wallet alone out into dangerous territory, then Ikeuchi seen her entering his monster form naked and he didn't reject that. Ikeuchi felt extremely jealous, something that Claire scoffed over, not telling Shuichi how he felt seeing them.
Then Chair chosen Ikeuchi as a sacrifice, but didn't told him he was supposed to just lure Madoka group into toxic plants and that's it, betraying his trust.
Nobody tried to find Ikeuchi after he ran away, they only tried to contact him through phone but abandoned him, didn't look for him at all.
He walked alone in the forest for days, filled with other coin collectors.
Sure, he lacked confidence to confess his feelings to Chihiro, but neither of anyone else in this story so far so can't blame him for that, they're all dumb teenagers.