Hey remember this dude?
Yeah, Same guy, just after he mutates himself into a poison dart frog to keep from dying from that terminal illness he's got.
He can't fight, yet, but he's working on it.. oh uhh, he Bioengineered the frog himself to have some kind of control of his appearance and abilities. Didn't go 100% but its enough that he's happy.
I'm still sorting out how his poison would work, one thought is His skin is that of a normal frog, so he can handle animals and touch people without worrying about poisoning them.
But when he's dunked in water though, his skin becomes poisonous like a classic dart frog, basically rehydrating the poison, thus he can't really touch anything or anyone till he dries, which can take hours!
He tried to make the poison less potent before his mutation, but due to unforeseen circumstances, wasn't able to complete it, and upon mutation, found it was far more potent than he thought, so he has to find a way to deal with that.
Another is he can control it, to an extent, like secreting it like sweat when in distress / physically restrained, and has to wait hours for it to dry before he can touch anything.