How bad is cheating second... or third?

if your partner cheated and you stupidly forgave them, and they did it again with a different person that you know of. You are obviously in a toxic relationship at this point and should have been done with it but you're not. how bad is 1-10 to cheat on them with someone in retaliation? Is that still cheating?

Updates
8 mo
I ended the relationship with him like 8 months ago that could be its own post because it went up like a dumpster fire and really ended with an order of protection
How bad is cheating second... or third?
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