I feel like any kind of confrontation between the two would just end in a stalemate. Both have insane defensive abilities, but the best one can do is manipulate and shoot the other, while the other is really, really good with a sword. It's just that Dan is immortal, and Richard can physically stop anything. I think I'd give the manipulation the edge, simply because it actually has more than a 0% chance of working.
Dan has only been shot really and both times seemed enough to incapacitate him (only time he pulled shenanigans was in Trapped 1 where he just got up like a second after and KOd the guy) other two times he seemed out of it. Besides who is to say Richard could just chop his head off and pull a "Hidan" sure Dan could be alive as just a head but not much he is gonna do cept try to convince Richard to kill himself or something which isn't going to work I think.
also one could interpret (though it could be wrong cause Trapped seems kinda random) is that the drug wears off after a time (hence why he wanted the girl to take it) though then again that could be just because he just wanted someone to have sex with and she never really took it.
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