Out of all the characters in Marvel's library, Spider-Man certainly has the best selection of villains. Time and again, writers and artists have been able to call upon the likes of Green Goblin, Mysterio and Venom to torment the wall-crawler through various different means, but perhaps the most storied antagonist is Doctor Otto Octavius - Doctor Octopus.
Doc Ock has been battling wits with Spider-Man pretty much since the hero was first introduced, and it's often been the case that what drives him (a fierce rivalry with the web-slinger, as well as a somewhat unspoken respect), has resulted in the pair's confrontations getting more and more serious with each encounter.
Sure, the likes of Venom and even Green Goblin may hate everyone's friendly neighbourhood web-slinger, but they are both victims of their own lack of imagination. Octavius, on the other hand, is as close to an evil genius as you can get, and vows to outdo himself with each and every battle he and the wall-crawler partake in. This has resulted in some truly egregious acts over the years, and though none were quite as destructive as the Goblin-orchestrated Clone Saga (at least in terms of sparing readers any unnecessary convolution), most - if not all - were certainly more compelling.
If nothing else, though, these acts prove one thing: the wall-crawler may have plenty of great bad guys, but Ock is by far the best.