Well, if it is none other than Venom itself. I guess it shouldn't come as a surprise that the final boss in a video game also happens to be its best one as well. After all, final bosses provide the last chance to use every power/item you've earned so far against an enemy that's supposed to push you to your limits. Granted, there are some exceptions like most Soulslike games where their best content isn't even related to the main story. However, Marvel's Spider-Man 2 plays it safe and saves the best for last.
Venom is truly a powerhouse. He can kill Spider-Man in just a few hits, and the web slinger's attacks barely inflict any damage on him. If players hope to beat him, they need to bring their best game and make use of Spidey's symbiotic powers at strategic moments to do constant damage without spending a lot of time recharging their abilities. Being on the lookout for any source of high-pitched sounds (such as car alarms) to stun Venom is also key. Otherwise, the Lethal Protector can be an unforgiving opponent.
The fight is filled with a lot of jaw-dropping moments like Venom growing wings or switching between Miles and Peter to try and fight him off. The environment also plays a huge part in making the sequence feel grand and cinematic. Getting to battle an alien in a football stadium lifted high up in the air by symbiotic tentacles plays as awesome as it sounds. Besides, the soundtrack playing in the background is nothing but perfection.
Overall, Insomniac truly did Venom justice. Getting to fight him was the perfect way to end Marvel's Spider-Man 2, and we can't wait to see what they can do with the Green Goblin in a possible third entry.