The avatars don't have health points and the simulation lacks death mechanics like a traditional MMO.
Griefing is typically achieved by placing garbage objects (if permissions allow building) or making hideous, obnoxious, obscene, and/or performance tanking avatars and ruining the look of a space.
Ultima Online, offered more freedom already in the 90s than most modern MMOs (of course freedom in gameplay doesn't necessarily mean "fun" for most players, but still UO pretty much invented the modern MMO genre, then WoW "tamed" and simplified it which made MMOs hugely popular, and in turn it was WoW - not UO - that everybody else copied).
Avatars do have health points, and it's possible to get killed, but only in combat areas. Those exist, as games within Second Life. But ordinary residential, retail, and display areas have that feature turned off.
