I am a big fan of the Infamous games. While all three have been great (I've not yet played Last Light), the first title stands as my favorite yet. A big reason for this, and I will be spoiling the end game here, is Kessler. Kessler serves as the antagonist of the game, and his fight stands as one of the best final boss fights in gaming.
There are three big reasons this fight works so wonderfully. The first one being the build up. Slowly, as the game goes on, Kessler begins revealing himself to Cole, our hero. There is an ever growing personal grudge you begin to foster with him. Two points closer to end game things begin to seriously heat up, being when your best friend Zeke turns traitor and hands over the Ray Sphere, and then when you enter into a rigged choice that will see the life of your girlfriend end. Kessler has spent a lot of time isolating you and forcing you to grow distant from all those around you. Things get weird when he essentially talks about grooming you into a Hero and tries to convince you to use the Ray Sphere again, killing several people but amplifying your own power. There is a lot of tension and intrigue built by this point. Clearly, you are meant to hate this guy, and for good reason, but for some reason, he wants both this and for you to grow in power exponentially.
Then comes the actual showdown with Kessler. When you finally confront a mortal enemy as it were, it is always disappointing when you get a lackluster fight. This fight, however, is a damn good pay off. Kessler's combat abilities are impressive, and he seriously comes across as this powerful juggernaut the game has been building him up as. A fierce Multi-part that I found both challenging and visually stunning. This was precisely the fight I was hoping for with Kessler.
Finally, comes the post-battle Reveal. You and Kessler are the same person. I won't lie, I don't like how you never really gain an idea of how the fuck he traveled back in time and this creates all kinds of logical paradox's one could conjure up with many time travel stories, but that's a bit par for the course with time travel. But back to the point, it immediately re-paints everything you thought about Kessler. It's now almost hard to hate him, it becomes more a mix of admiration and pity. You realize just how difficult it was for him to do all of this to you because it made the people he too cared about suffer, all for his goals of saving a world from 'The Beast', something that will be the focus of the second title. It wasn't just you suffering when Zeke betrayed you and your girlfriend died, it was Kessler as well.
Moments like that reveal need to be built up and earned. Were it not for the slow build of information on Kessler followed up by hard-hitting moments with Zeke and your girlfriend, mixed in with his strange dialog that implies he has a great deal of care for what you decide to do, followed up by a legitimately epic boss fight, that reveals would have meant nothing. (Well, the boss fight may not have needed to be so awesome, but it certainly helps). Big moments need a build to leave a lasting mark, and this is something Infamous did amazingly well.