"Best" and "What I Like Most" are two very separate things. In fact, "Best" tends to be very hard to define.
Take Mad Jim Jaspers [http://marvel.wikia.com/James_Jaspers_%28Earth-238%29], for example (a creation of Alan Moore, if I recall correctly). One of the most powerful mutants in any reality, capable of manipulating reality on a pan-dimensional scale. Think Scarlet Witch on crack. Downside? He was fucking insane. Not to mention his very existence was ripping reality apart. Eventually they had to destroy his entire universe to kill him.
OK, OK, that's a little over the top. Let's take...I dunno, Nate Gray [http://marvel.wikia.com/Nathaniel_Grey_%28Earth-295%29] for an example. You said you liked Cable, right? Well, this guy is what would happen if Cable didn't need to restrain himself to hold off the T-virus. The result? He's the strongest psychic alive. Telekinisis, Telepathy, Astral projection, the whole works. He inherited his father's energy blast powers, too, only strong enough to rip a planet in half. Downside? He was supposed to die before he turned 18. I say supposed to because, through some wacky hijinks, he managed to not be...well, dead.
So...yeah. Game-breaker powers tend to come with a massive cost. Just sayin'.