① Willing: You are completely willing from the beginning in this affair, out of cruelty or something else.
② Reluctant: At the beginning, you are not consenting to this without either serious coercion or blackmail. Yet, as time goes on, you become willing. Maybe even more so than the initially willing person.
③ In Love: This is the fluffy, romantic prompt. You're in a relationship with a person you don't love, and you're cheating with the person you really care for.
④ Too Good: You don't want to keep this up, but the sex is way too amazing.
⑤ Drugged: You're addicted to the drugs that make you addicted to the sex.
⑥ Prostitution: This was at first a way to make money; now, you like your work.
⑦ Slutification: Once, you were such a nice, pure person. These days, you're modified into the type who'd just love to be fucked and show it in all the lewdest ways.
⑧ Trying to Stop: You can stop seeing them in secret at any time!
⑨ They Give Me Nothing: Your significant other can't satisfy you at all because of lack of time, lack of attention, or lack of endowments.
⑩ No One Can Do It Like You: Only your illicit lover can make you feel this way. There's no replacement.
⑪ Age Difference: You need someone younger than you with more stamina or someone older with more experience.
⑫ Forced to Watch: The person being cheated on is brought in to watch against their will, usually by extreme force.
⑬ Brainwashed: You love this because someone's screwed with your head.
⑬ Consensual: Actually, the person your with knows all about this and encourages it. You're swingers!
⑮ Fucked Silly: You don't know what you want in your own addled mind.
⑯ Pushed Away: You wouldn't do this if your lover didn't ignore and hurt you all the time.

① Because I Can: There's no real reason to take this person from someone aside from seeing if you can.
② Revenge: They ruined your life...you'll ruin theirs by tearing apart relationships.
③ To Hurt the One You Love: You want to get the best of your enemy, and to do this, you're turning their closest person against them and dependent on you/adoring of you.
④ If I Can't Have You: You wanted this person in the past. Now that they're with someone else, you don't want them, but you don't want them to be with their significant other, either.
⑤ One-Sided Love: Your intentions are pure. You love them, and they should be with you! They just don't know it yet.
⑥ You Belong to Me: You're not the person's main squeeze, yet you want to be and you want everyone to know that you're having sex. So you're marking them up, not being subtle, having sex in risky places...
⑦ Impregnation: The ultimate show of ownership is pregnancy, so you'd love to get your secret lover with child and get away with it all.
⑧ Brainwashed: You'd never steal someone away normally, but you're under the influence of evil.
⑨ Ruin You for Anyone Else: They'll never find pleasure with others, no matter what.