Look, I concentrated on single-handed, smithing, heavy armor and shield, with a little effort invested in archery and sneak, and I think one perk in Restoration. I maxed out the four main skills, I think, somewhere around the high forties in character level, with two thirds of my levels going into endurance and the rest into health.
And while I was a serious ass-kicker by that point, I wasn't invincible. I couldn't just stand there and take hit after hit like I was from Krypton or something. I could take on giants and dragons and mages and bandit gangs and win, but I couldn't just go running around willy-nilly. The challenge still remained in the game - even on Adept skill level. I distinctly remember one fight against three or four mages that was a real corker even with my degree of power.