That's not my question. It was: "When has Mewtwo started a fight, instantly read their mind and mindhaxed them?"
Sounds more like CIS than PIS, because i'm fairly certain he never uses his mental powers offensively in a battle. Pride? Stupidity? Who knows. But it is a character flaw like Gremmys.
Also as far as i'm aware he cannot manipulate time. If so i'd be glad to get a source on that
You see, what you're doing, is instantly putting Mewtwo in a best case scenario, where he makes all the correct choices, ignoring the fact that hes in character, and will just make all the right moves in battle whilst Gremmy makes all the wrong ones.
The only reason this fight is not a outright stomp is because Gremmy tends to not make the right choices.
Imagine what would happen if I took your approach (No Pun Intended)
"Gremmy imagines Mewtwo is dead,Or that he didn't exist in the first place, Gremmy uses Vanishing point and Erases His presence from the world then kills Mewtwo, Gremmy erases Mewtwos power, Gremmy turns Mewtwos body into cookies, Gremmy BFRs Mewtwo into Far out Space, Gremmy Imagines 10 Mewtwos to fight Mewtwo."
Well i'm sure you get the picture.