I agree with the others but especially what Belle and Rhionnonsmoon said. This has reached an unhealthy/deceitful level. You've done this before. He's made it clear he doesn't want contact, so if he knew this was you, he would be very upset.

If you 100% didn't like a guy, it would be wrong of him to befriend you online. Don't tell him and just delete this identity. Don't look at his activities online anymore.