Anyone with a high Bluff or Diplomacy skill. It just feels like a cop-out when with just a few words you can end entire encounters. A friend has a Gnome Wizard focused on illusion spells and has a Bluff that's through the roof. Yeah, technically enemies get a Will save to disbelieve, but against that Bluff, no they won't. I'm not saying it isn't effective, but it's maybe a bit too effective and a bit anticlimactic when one spell solves an entire combat.
Reach builds with high STR. Another friend has an Abyssal Bloodrager with the Rageshaper archetype. His claws pratically one-hit everything that threatens from him. Of course, he's specialised in reach, so at some point he had 20-foot reach. To be fair, his AC is terrible, but as said, most things are dead before they come within melee contact.
Another friend has a weird build where he transforms into an octopus with 8 attacks. I don't know the build exactly, but his damage output was amazing. The only downside is that they're all secondary attacks, but he still managed to mitigate most of that.
I like powerful builds, but some of these are really over the top and take the challenge out of the game. I make powerful characters as well, but I don't go out of my way to finish fights on my own. Most of the ones I listed here could take a scenario and solo them, given enough time to prepare.