He really was just... Walt, in this episode. Total ego trip, building something up for himself and in a moment's notice, tearing it down in his own hubris.
The phone conversation with Kim just setting him off into this descent that I honestly never saw coming is breaking my heart.... and once again fulfilling Chuck's cyclical, age-old prophecy about good ol' Slippin' Jimmy.
Gene conning the cancer patient is gross and heartbreaking in the way that him conning Irene was gross and heartbreaking, and conning Chuck was gross and heartbreaking, and conning Howard was gross and heartbreaking. And speaking of Howard, Jesse's "Who's Lalo?" really made my skin crawl. This also totally reframes how Saul saw Walt, the sort of walking dead cancer patient that he can play to his own tune. Only we know things don't go that way in
Breaking Bad, but as Gene here he still uses that same slimy philosophy to make himself accept what he's doing, telling himself that the guy will be dead before he even knows what hit him. He bit off way more than he bargained for with Walt, but with the mindset he's in now, rejected by Kim and with nothing to lose, looking down on this guy that he (seemingly) KNOWS he can take advantage of?