Wrathful Smite
The target takes an extra 1d6 Necrotic damage from the attack, and it must succeed on a Wisdom saving throw or have the Frightened condition until the spell ends. At the end of each of its turns, the Frightened target repeats the save, ending the spell on itself on a success.
Using a Higher-Level Spell Slot. The damage increases by 1d6 for each spell slot level above 1.
Wrathful Smite 5.5e 2024 vs. 5e 2014 edition differences
The 2024 version deals necrotic damage instead of psychic, applies the Frightened condition with a recurring save at the end of each turn, and increases damage by 1d6 per spell slot level above 1. The 2014 version only requires a single Wisdom save to end the effect.