I'm going to go out on a limb and suggest the most powerful character (based on my experience) would be a sneaky archer.
Light armour over heavy to help with necessary escapes early in the game, and because you can get to the armour cap no problem with even elven armour later in the game. The overpowered combo of smithing, enchanting and alchemy- maybe only taking smithing perks up to elven or glass. Enough speech perks to sell anything to any trader, but ideally investor too. Almost all archery perks. Most sneak perks
The character would be insane by about level 45, but also not too bad early in the game when it's more difficult. Hit and run (or rather hide) style sneaky archery is time consuming and doesn't work too well against an opponent that can heal themselves, but with alchemy and sneak you could pop an invis potion and sneak right past tough situations and occasionally steal important items instead of fighting for them. Wild encounters could be tough but with a bow and paralysis/slow potions you could at the very least escape pretty easily
You could add some dual dagger ability to this build but I only think it would make it worse since pure archery means all of your enchanted items are geared at defence or archery, and you also wouldn't have to spend any perks in the one handed tree or waste any time training one handed. For fun the variety would be nice, but for a straight up overpowered warrior I'd stick with archery
