Fantastic Four (1961) 215-A

"Blastaar"

Reed is helping an old friend with a science experiment that goes wrong and the FF leap into action to save the professor from certain death. Before they can analyze what went wrong, the FF are called back to the Baxter Building by an alarm set off around the portal to the Negative Zone. As the FF head back to check on the alarm, Dr. Randolph James is brutally attacked by a street gang and left for dead. He contacts Reed but instead tries to use his failed experiment, an evolutionary advancer, to heal his wounds. The result is Dr. James is transformed into a very powerful creatured. Meanwhile, back at the Baxter Building, the FF run headlong into the fury of Blastaar, who has emerged through the portal. Blastaar manages to escape, with the unwitting help of Johnny, as he disappears into the streets below. Reed returns to help his friend only to discover his friend's transformation. Reed convinces James to head over to the Baxter Building for an examination. Along the way, James gets revenge on the gang that left him for dead as he turns them into rats.