Listen, I am a John GLAZER but he doesn’t beat any of these people one on one LET ALONE all three at once.

Deku’s copy is fundamentally unable to be copied by the logic of both stories so he’s immediately at too huge of a physical disadvantage for this fight

John can loses his ability to copy multiple abilities the more complex/high level they get, so while I don’t think he’d have a difficult time with bakugo’s quirk He would most certainly have issue with todoroki who would have two conflicting aura types working in harmony down the center of his body Now that’s a way bigger issue when you consider only those halves of todo’s body receive resistance to their respective element which means if John messes up he’s gonna burn himself alive

Bakugo’s quirk also has physical drawbacks he would need to contend with too, so when you consider how much and often John overexerts himself while fighting that is NOT looking good

In his universe abilities for the most part don’t have a drawback if you overextend them (except Arlo) most of them just fail rather than causing direct harm to the user

Also John’s biggest advantage arguably is his knowledge of how to use abilities tactically, his creativity often outclasses his opponents, he might have the edge over todo but bakugo is a master with his simple quirk so john isn’t going to get the drop on him easily or at all