Honestly, someone killing you while you're LD and/or killing your familiar is a pretty low bar for "griefer".
Here are some things I think rise to that level:
1. Looting and/or destroying stuff you don't need and are unlikely to be able to trade after you kill someone. This assumes a reasonable definition of "need". This also includes situations where there's an ostensible RP reason to loot/destroy the stuff (e.g. "it bears the taint of magic/evil/civilization") that is unreasonably flimsy.
2. Killing someone repeatedly in quick succession. The definition of what constitutes "quick succession" is up for debate.
3. Using your powers as a cabal leader to jack up someone's character for "no good reason".
4. Breaking RP to kill someone, *especially* when the kill was facilitated by the target's (faulty) assumption that you're following reasonable RP.
5. Consigning an enemy to waste a bunch of time. For instance, summoning a rager into a locked room then wording without even trying to kill him when there's nobody online to let him out.