Because of His high damage and Her low healt she is easy to counter,but if she is in use of a pro she can be very annoying.If your enemy is a good Evie player try killing her with traps around her ice block or kill her when she cant use her attaks.
Use your CC immunity legendary when facing him and use your totem whenever you see BK use his bomb. This can help you counter stun reliant champions for you and your team.