Gather damning video/voice/text evidence. Do not show your cards to anyone, not your friends, kids, relatives, or coworkers. Not even a hint, people have big mouths. Hire divorce lawyer. Only reveal your knowledge of her infidelity to her after your lawyer tells you it is time. After you've won your divorce case, you may now plot your revenge. But remember, you'll automatically be suspect #1... so best to just let it go.