You may laugh at 1 in all levels but I once created a level 5 magic user with 1 level each in Cleric (death), Sorcerer (shadow), Wizard, Druid and Bard.

He had a passive AC of 18 and a buffed AC of 25 (SoF + Shield reaction).

All the same spell slots of a level 5 character but with a LOT more spells (but nothing above level 1, everything was upscaled).

Shilleileigh meant he was hitting well in melee and because of Death Cleric + Toll the Dead + Cantrips scaling with CHARACTER level and not CLASS level he was doing 2d12 damage to TWO enemies (so really 4d12 per round in close-combats given a lot of enemies have terrible WIS saves).

This wasn't even a min-maxed character at all. He was a serial con artist so had the Actor feat and, because I played him as a secret death cult guy, also had absolutely no healing other than goodberries.