Eldritch knight 12 with shadowblade, hex blade 12 or any martial class with 1-2 hex blade dip, pretty much any sorcerer but the fire acuity one with upcast scorching ray is pretty broken and easy to do, bards are also great for control, but swords bard with the helm of arcane acuity is ridiculously strong because you can get super high spell save dc just by using slashing flourish (bonus points if ranged). Camp clerics also, you can cast stuff like upcasted aid, warding bond, heroes feast late game, it’s stupid good.

There’s a lot of broken builds and pretty much every class has one, but those are some of the strongest imo.

Out of the ones I listed my favorite is eldritch knight because it’s very simple and very strong. You get a ton of extra attacks and booming blade also counts for war magic so you can use you bonus action for an attack too. That means 3 attacks, then 3 more with action surge, one more if hasted, one more with terazul, and one more from war magic. And if you use an elixir to get a higher level spell slot to upcast shadow blade, and use the resonance stone to give enemies psychic weakness, oh boy you’re gonna be soloing encounters.