Negative friendship. Instead of just remaining acquaintances, if you do enough harmful things to any one villager, you will eventually start filling up their social bar with Blue Hearts. Blue Hearts do the same as Red Hearts, they unlock more events the more you gain. At 8 negative hearts on marriage candidates you will be barred from ever romancing them in that save file, and at 10 on normal villagers they can no longer be befriended.
They will send you threatening mail and may even sabotage your farm by destroying your crops or releasing your animals. Shopkeepers will jack up their prices until they refuse to serve you at all, and you will stop being invited to all events.
Make enemies of everyone, and they will just torch your house and kick you out.