Does anyone have a list of preferred natures for all the legendaries?

Well, it depends on what you want to do with your legend. Like, Jolly Mewtwo is horrible normally, but if you're turning it into Mewtwo-X it's great. Some pokes like Primal Groudon can have a decent set with just about any nature... except neutral, neutral nature is always ass.

Adamant/Jolly
Timid/Modest

>>30107572
Look at their stats, look at their movepools, and from that information determine which nature would be best. It's not that hard op

>>30107572
Buzzwole Adamant
Xurkitree Modest

>>30107709
Nah, you want Xurkitree to be Timid

>>30107849
Oh yeah that was my first thought. You want a Modest Magearna. Sorry.

I have months worth of event legendaries stocked up to soft reset for natures