Powers: None on his earth of origin (Earth A). When this MacDonald Gargan travelled to Earth-616 through Albert E. DeVoor's Atomic Resequencer, his molecules were realigned on an atomic level to match the structure of that Earth's (Earth B) MacDonald Gargan (Scorpion). Therefore, he possessed all the powers that Scorpion of Earth-616 possessed.
Bio: Was one of the characters in She-Hulk #21 that travelled from Earth A (his Earth) to Earth B (regular Marvel Universe) on a vacation as his Earth B counterpart. Was eventually discovered and with the help of Jennifer Walters, She-Hulk (Earth-721) and the Mr. Fantastic's of Earth A and B, was sent back to his dimension of origin.
Notes: Earth A's MacDonald Gargan must have gone through the Atomic Resequencer before Earth B's MacDonald Gargan became Venom and was still under the identity of Scorpion. Therefore he must have been in the regular 616 Marvel for some time, although he wasn't officially discovered until She-Hulk #21.