Why do you wish to hurt the woman at all? She wasn't the one in a committed relationship with you, she broke no vows to you. Your issue should be with your husband.
You need to ask yourself some hard questions. Do you want to punish him & yourself & leave? Or do you want to find a way to forgive him & stay?
If you are working toward staying then you need to figure out why he felt a need to step out in the first place:
1. Is he just a man whose nature will never let him commit to only one woman? If so, there are things you can try but it isn't likely that any will be a permanent solution.
2. Was there a lack of intimacy at home that left him needing to look elsewhere? If this is the case you may need to do some work on yourself to step up your own sex drive. Look for some sex magick that will be effective & fun to execute at the same time. Leave him knowing he cannot find any better anywhere else. A faithful man who is worn out by his woman at home isn't likely to go dipping his pen in another woman's inkwell.
3. Was he just lured by a temporary temptation? You can look for spells to tie his nature so that he won't wander & will keep it at home.