Yeah, the Vamp fight in MGS2 is definitely my favorite boss in the series so far. He's pretty damn cool, it takes place in a cool area, and most importantly it's really f***ing fun to play. The Ray Army and Fatman are both awesome in theme and gameplay, too. Solidus fight is a great way to end the game and is good gameplay wise because it gives you a boss fight to use the sword in. Olga is just kind of "eh" but it's so early in the game so whatever.
There's definitely fewer boss fights in MGS2 than the other two games but they're definitely higher quality overall.
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[NO BARKLEY NO PEACE]
im here to you dark soul with my LIGHT -ertyu