It's clear Canelo Alvarez doesn't like Gennady Golovkin ... 'cause the boxing star tells TMZ Sports GGG is a straight-up "a**hole" who talks too much -- and he's planning to KO the guy because of it.
"He's a f***ing a**hole," Canelo said of his upcoming September opponent. "He's not honest. He pretends to be a good person and be different but he's not."
Canelo says his opinion of Golovkin basically boils down to this -- he believes the 42-1-1 boxer is just flat-out two-faced.