Seth Rollins just went in on Logan Paul -- saying he REALLY doesn't like the guy ... while adding that the former YouTuber should leave the WWE and go back to "buying counterfeit Pokemon cards."
The WWE superstar unleashed on Jake Paul's older brother during an Instagram Live sesh on Friday ... just days after the 27-year-old shockingly eliminated him from the Royal Rumble.
Rollins insisted he ain't alone in his dislike of the WWE newbie ... saying other wrestlers can't stand him either. He then questioned Paul's real reasons for joining on with the org.