Claims to have fought Bane and Doomsday simultaneously before waking up in a puddle of his own piss due to their bladder-disrupting powers. If Dipsomania was a power, he'd be unbeatable.
For most of his appearances, Six Pack just boasts about a lot of unbeleivable claims to past superheroic glories, but for all intents and purposes he's just a short, fat, middle aged slob with delusions of grandeur. His most dangerous combat maneuver we ever see is him going after somebody with a broken beer bottle.
Six Pack actually leads a team of like minded delusionals and miscreants with seemingly good intentions, a misfit hero team called Section-Eight. Section Eight successfully assists Tommy "Hitman" Monaghan in getting the bounty Hunter Lobo off his back.
In Section 8's final battle, most of the team is slaughtered by demonic beings while Six Pack, who is pretty much the last one standing, is protected from the demons' blasts by an unknown power. This is either the pure projection of Six Pack's heroic soul, or an actual super power, or a flat out deus ex machina. Nevertheless, the demons respect Six Pack's heroism at this point and transport him to another reality for some epic battle; their exiting for this by all acounts saving the world (or at the very least Gotham City). Hitman presumes Six Pack dead at this point. He is wrong. Six Pack emerges from his battle victorious and reformed; no longer in superhero garb, now going into Alcoholics' Anonymous.
Recently, however, Six-Pack began drinking again, as well as reforming a brand-new Section 8.