A few examples would be:

[Joke concerning one of your family members] "Thanks man, ... lost his/her battle with cancer yesterday."

[Toxic teammate] "I'm new. My grandson got me this game. Sorry for making you lose."

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I could go and on but most of them are all really situational. These two examples should be enough to give you a general idea of how you can most efficiently make a troll feel guilty.

For the best effect, just leave directly after leaving your message. You don't need to be there for the aftermath since this is something that will stick with the troll for many years to come. In some cases, the troll might only realize how insensitive he was a few years down the line.

Guilt trips are very manipulative and hurtful. This is definitely morally wrong and you really shouldn't do this, but I'll turn a blind eye considering how that's what a troll deserves.