Warpiglet
Adventurer
My preference is the tanklock version of the pact blade. Fiend Patron, Max out Strength first (16 or 17 with feat), charisma is usually a 14 to begin with. Variant human, feat: Heavy Armor Master (+1 str, DR 3). First level is fighter, the rest are Warlock. Wear plate, use a heavy weapon (Greatsword, Greataxe, Maul). Take Great Weapon Master when you can (either at level 5, or level 9).
You focus on using Armor of Agathys and various damage reduction techniques (DR 3 from Heavy Armor Mastery, Blade ward when appropriate, etc), and lay into them with your weapon, daring them to hit you. By the time they eat through your Armor of Agathys you should be starting to drop them, giving you renewing temp HP.
Upside: an incredibly resilient tank at low levels, and strong up through at least lvl 10. Fantastic against hordes of mooks.
Downside: Weaker against ranged attacks, and single boss monsters. I also suspect your lower AC will be a bigger issue above level 10 when the big monsters start hitting incredibly hard.
I have taken variant human with moderately armored with highest scores in STR and CHA. I also take a greatsword! I took fiend for spell selection (fluff wise was trained by and then betrayed a night hag! Good times.
I am currently looking at a hexblade in a similar vein but am thinking about a mace and shield for the look of it (he will be a fallen cleric perhaps). Cannot wait!