In my current Skyrim playthrough, I did something I had never done before...
KILL PAARTHURNAX.
I feel like ***because I did it. The Greybeards hate me, I can't reset which word of power I want to meditate on almost at will, and what do I get for it? Three NPCs that're supposed to "help" me kill dragons, another NPC who's supposed to give me dragon-slaying quests, a shitty -25% melee damage from dragons perk...
And sadness because I found Paarthurnax to be more useful to me than the Blades turned out to be.
Yeah, The Blades could have done something useful like built up a rebellion against the Aldmeri Dominion but instead they decided that all dragons had to die "because Alduin."