Vengeful Smite

While the blade is sated (once per short rest, max 1/2 your warlock level per day), you deal extra force damage to the target in addition to the weapon’s damage.

The extra damage is based on your highest level spell slot (can include used slots), but does not consume the slot

2d8 for a 1st-level spell slot, plus 1d8 for each spell level higher than 1st, to a maximum of 6d8. The damage increases to d10's if the target has a good alignment.

The user can choose to push the target back 2*(user's warlock level) feet with a strength saving throw based on your spellcasting dc

Missing with a roll of (your proficiency bonus) or less causes you to loose your sated state until your next source of necrotic damage.