What stats does Radiant Last Whisper give?

Radiant Last Whisper grants 45 AD and +40% AS.

What kind of item is Radiant Last Whisper in TFT Set 17?

Radiant Last Whisper is a Radiant item in TFT Set 17.

Damage from attacks and Abilities 30% Sunder the target for the rest of combat.

radiant

Damage from attacks and Abilities 30% Sunder the target for the rest of combat. This effect does not stack.

Sunder: Reduce Armor

Armor

The physical-defense stat that reduces incoming AD damage. Tank items, the Bastion trait, and champions or items that grant flat Armor all feed into this mechanic, alongside the handful of effects that scale a bonus off a unit's Armor value. Sunder is its inverse — a debuff that reduces enemy Armor.