Inside the Park Home Run

Head to Zeleskos at 31.6, 47.2 to start a Trial of Athanos. The achievement can be completed on the Trial of Courage as well, not just the Trial of Wisdom as the tooltip states.

Athanos will perform a Power Swing — a front cone attack that deals heavy damage and knocks you back. You must survive five of these to complete the achievement. Do not stand near the edge of the arena when he uses this ability, as the knockback can throw you off. Step to the side to avoid the damage while still letting the hit register.

Athanos will charge directly at you. Dodge sideways to avoid it, and position him so his charge does not carry him across the entire arena. This keeps the fight manageable between Power Swings.

Athanos will kneel and begin recharging power while a rotating shield circles around him. Move to the unshielded side to continue dealing damage during this phase.

After surviving all five Power Swings, defeat Athanos to earn the achievement. For the easiest approach, keep him deep in the open space of the arena and use the extra room to recover from knockbacks and dodge charges.