From my experience no one wants to be stuck in a combo movie for the entire match if they are a complete noob. People who I don't know that well, or are friends. I generally just relax, and take it easy during the fight. I can't really find it in me to purposely lose. But I'll not finish combos, or do small punishes. Wait and let them act for a bit. So they feel like they have a chance. And the more they play and improve, the more I can slowly increase the difficulty for them. Let them ask questions, or whatever. If they talk trash if they win or something, that's when they get destroyed. This is only when playing in person.
Online, I generally just play however I feel like playing. I don't exactly feel any obligation to help them out, unless they ask. And online has been pretty iffy for MK Arcade Kollection, MK9, and Injustice. So it's rare to find a good connection in that anyways lol