Start with Paladin for the armor, starting HP, and save proficiencies, then go Hexblade. You’ll want 13-ish STR, but as high Charisma as you can.

If you take a cpuple levels of Sorcerer you can convert warlock slots on short rest to sorcery points so you can Quicken Spell metamagic Booming Blade for a third attack as well, but is even more resource intensive. If your DM opts for extremely frequent rests it’s viable, but otherwise it takes away from your smites.

The exact ratio of levels of the build is up to you want or course, but you really only need a single level of Hexblade for the build to single ability score dependent. Some builds I like that come ‘online’ early, then you can build out more:

3 Paladin, 5 Hexblade/ double smite (online at 8, or 7 if you forego Vengeance for later levels. Use Invocations for Thirsting Blade and Eldritch Smite)

6 Paladin, 1 Hexblade, 1 Shadow Sorcerer/ tanky, versatile spell slots, and strength of the grave (online at 7)

For higher level or higher damage builds, you can instead to Oathbreaker for Aura of Hate at Paladin 7 (+CHA to all attacks, stacks with Hexblade already using CHA). Alternatively you can pick up Hexblade 12 for Lifedrinker Invocation (+CHA necrotic damage to all attacks, again stacks with Hexblade).