See he himself said that you can't trust Ella, he's aware all of this time, but his dumbass trusted Ella, well because Ella gave her powers and he got manipulated just like Jake yada yada yada. He is not getting "Mindfucked" because he CHOSE to trust Ella.
The mindfuck is just a small part of all these corrosion, it's actually almost not that effective to Deryl. Deryl is just stubborn at it's best.
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See, he even proceeds to continue to fight the Mc because of his stubbornness. If he's REALLY MINDFUCK at best, Deryl will stop the fight and asked what the fuck is happening and why is he a monster full blown monster. But it didn't happen, he's fully aware of his action and what's happening throughout all these time. All of these can prevent if he's not stupid and stubborn, he just wanted to get beef with the Mc.
Until he regain small memories from the "Doll" and almost got beaten up with the Mc, and now he's done with her.
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So, don't tell me that Deryl is getting mindfucked at the fullest, it's not a reason, because, Well jeez Jake himself already said that the imprinting is not complete, it's actually easy to understand. It's just that Deryl is stupid and stubborn until he realized he's fucked.