1) Try something different
This is about challenging the assumption that full looting is "terrible" and makes me a horrible person and all of that stuff people throw my way below. That line of looting vs. not loot just isn't as black and white as people want to pretend it is.
2) Revenge story
Who doesn't like getting revenge on someone who mistreated your character? Imagine you got fulled, then had the chance to return the favor. That can be a great story for your character.
3) Get people to work together to gang me down (that one is OOC-ish)
I don't know why that doesn't work. Probably because we've all gotten stuck in Rambo solo killer mode, but why don't people recruit allies to help? Why didn't this mage get the duergar or the assassin to help? Ideally it would encourage more social play. There are some comments below talking about with higher player numbers, you could get an ally and gang someone down to regear or get handouts or whatever. I think this is still possible, but people don't do it, and I think that is a problem.
4) Gear and prep circulation
This is why I made a thief and not something more capable of actually landing kills. The ability to strip preps and extraneous gear from people and put it back into circulation, either via ragers (who tend to die alot) or Tahren (which puts it back on NPCs and gives people a reason to go try and get it again). I mean when people basically farm a prep until it is maxed and then horde that prep religiously like some sort of crazed Russian (I'm directly poking fun at Beront, in case that wasn't clear), you've got something broken. I wanted to remove the ability to do that fairly directly. Died at the Big D and go crazy to get your Hell gear back? I don't think so. That shit is gone. Go get some other gear.
6) Start a conversation about it
Probably the only real success. A bunch of people have stuck to the full loot is terrible line, and some have go full on the other way, but hopefully some see that it isn't as black and white as the community was pretending it was. Matrik has a point that if full loots are a time waste, so is and PK, and con-loss, and breaking up a ranking group with attempted PK. As Grokko, how many ranking groups did you ruin in FoN and Trolls even when you didn't land a kill? How dare you waste someones time! Full loot maybe crosses the line of being a dick in the general sense, but it isn't a well defined line and any number of behaviors can cross it depending on the dynamics of what happens.
There are some videos about asymetric character design I might post about, but they outline how everyone wants to fill their niche and have stuff that is specificly tailored for them. But with the level of preps available and gear that makes you crazy strong, a character can become a one person wrecking ball and fill a bunch of niches... that crowds out the classes design for those. As an example, if you have strange bracers and can permalag fairly reliably yourself... Why would you ever need a transmuter ally? Spiderhands, fly, enlarge, reduce, haste, detect invis, limited healing, damage reduction, fearie fog/fire, pass door, even slow under some circumstance... These are part of the core niche of muter, but you don't need them for any of it. Just gather the prep.