By taking the Variant Human race, this character can get the Sentinel feat at level 1. The Darkblade Warlock can then approach an enemy and attack with advantage since the enemy cannot see them.

Thanks to Pact of the Blade (and Hexblade), warlocks can be very effective at melee combat or even be an effective hybrid that works at all ranges. That said, a great option for a melee warlock is the ...