D'arby's powers are threefold: personal reality, soul removal, and mind reading. He is able to transport himself and others to a small island area, where he has a TV and video games. This is pretty instantaneous and just like 'put up a portal, oh I'm in there, you should come too'. During that transit, he's able to remove a small part of a person's soul - Jotaro's limb in the case of his encounter since he's a punchy punchman - and if you just punch him, boom, that's gone forever. He is able to completely take the soul of anyone he is able to beat in a competition, of which he chooses video games. He is naturally good at video games, and is able to read the mind of opponents to lull them into false confidence and perfectly read their strategies.
Essentially it's "can you beat man at video games. He always has leverage to make you want to play video games with him. Also he can mind read". Figured it'd lead to actual cerebral competitions and would work as an anti-meta character.
but he's also meta because some characters are from video games. if he's matched against mario and mario chooses smb 1, will mario automatically win? will mario dissolve into an existential crisis because his life is a game?
we can just theorize how good characters would be at video games but that's less fun ---
Video Game Music Contest 14 winner: Terraria Calamity - Scourge of the Universe