What made Gabriel more powerful?
Previously, Gabriel had to hunt down and lobotomize his target to take their power, whereas Peter automatically copied the powers of anyone he came in contact with, whether he knew it or not. With the exception of the odd ability (cryokinesis, super hearing, metal liquification), Peter could do everything Gabriel could do, and more (recall Peter could manipulate space-time, Gabriel would have had to lobotomize Hiro to do that).
I'll agree Gabriel was more ruthless and cunning with his abilities, Peter was more naive. But in the end, until his loss, Peter was technically more powerful.
Now, it seems Gabriel absorbs abilities in the same manner as Peter, and also has taken on his trademark empathy. This newfound regard for human life will make him a bit vulnerable, but I think he's still as cunning as ever.
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