Or if someone does something that you are really grateful for, you might write, “This is the kindest thing anyone’s ever done for me stg.” Because STG is a slang term, you should only use it in casual conversation, such as texting a friend, rather than in a formal setting. Example...
Stg, also written as STG, is a text abbreviation that stands for “swear to God” and is used to express passionate belief or intense exasperation, as in I stg