I sprained my ankle 2 years ago, and the bruising did not go away. I sprained the same one again a couple months ago, and bruising is worse.?

Chronic instability. Have you ever had any steroid injections? They can leave skin discoloration. Otherwise you may have suffered some underlying skin damage during the initial injury. Obviously there may also be ankle instability problems which have led to the second injury as well. It would be important for you to have a thorough examination and likely imaging studies with x-ray and MRI. .
Bruising wont last. Bruising is bleeding under the skin and wont typically last 2 years. What can change are the tissues under the skin which may appear darker with time after trauma. The biggest issue with repeat ankle sprains is incomplete healing of the ligaments or laxity leading to recurrent ankle sprains. You should seek out a local podiatric foot and ankle surgeon (www.acfas.org) for a complete evaluation.