[Neomi]

Interesting idea, Pyrenk. I've seen lots of threads on "best weapon" or "most damage" but not one like this.

Obvious things: High dex, High con.

Fighter-types probably have the most options as far as heavy armors, etc.

However, don't forget about CLERICS. If you followed the thread by Rataxes on Thomas the solo cleric, the possibility for protection spells, heavy armor, etc made him a pretty resilient tank. If you are soloing, think about a single or multiclass/dual-class cleric for this reason. If you're in a party with a cleric it doesn't really matter since you can just have someone else casting the protection spells.

Druids have ironskins as well as protection spells. Jaheira becomes a pretty decent tank as the game progresses.

One doesn't usually think of a mage as a tank, but if you're talking strictly about resistences, a high level mage with appropriate protections is darn-near impossible to hit.