It's likely ROYALITY! That's the ONLY ones I can see as DANGEROUS to MC family if he doesn't "play along" (she was LIKELY engaged to him because they were EXPECTING her to be treated HORRIBLY, like that one with the FMC reincarnating as a Villainess right as she's being MARRIED to the FAT EGG SHAPED OLDER Prime Minister by her EX and the "Heroine" only turns out she LIKES older men and sees that he DOES have GOOD. So they end up becoming a HAPPY COUPLE! At the end it's shown when the duo found out she was HAPPY and CONTENT! The Idiot Prince tried to RUIN the Prime Minister, making it CLEAR they were EXPECTING her to be in a "unhappy marriage" as some sort of PETTY "payback" because she "DARED to interfere in their LOVE AFFAIR! Irony was the PM was the one who REALLY ran the Kingdom and only MARRIED FMC to "humor" the spoiled brat! The moment he CROSSED the line, he arranged an "arranged MARRIAGE" to an OLDER WOMEN EMPRESS of another kingdom for BOTH HIM and the HEROINE!)
Her engagement is meant to be PUNISHMENT because he was likely PICKED because of his "horrible reputation" which is HORRIBLY Outdated information! He'd likely be TARGETED because Royals tend to be PRIDEFUL IDIOTS who DON'T take being WRONG well (He SLIGHTED them by NOT being the scumbag they THOUGHT he was suppose to be essentially, stupid, but never underestimate IDIOTS with Power who tell you "Say the Sky is GREEN or ELSE!" Prideful NARCS are DANGEROUS when they have the MEANS to INVOKE their WRATH!