Junken arena is an arcade top-down fast paced hack and slash
Try to defeat as many enemies as possible before going down. When no more enemies weak to your element are left, your element will change, and thus the enemies you target.

Fire beats Electricity
Use your Axe Spin Attack to target and defeat the Warbots

Electricity beats Water
Use your Backstab Attack to teleport and backstab the Fishmen

Water beats Fire
Use your Pool to mark only the Fire Golems, use attack to snipe the marked enemies.