IMO I think S.A.B.E.R 2 because it's overall an awesome fight from mechanics, to the music to even the design of the boss.
But anyway, I made this poll to see exactly what boss would rise to the top and become the best boss of the TTK.
Please leave reasons and comments below and try not to be salty. [spoiler]Because I don't think a boss would be worth arguing over[/spoiler]
MrAlex2t signing out...
Edit 1: It seems Darkblade has taken a massive lead with 68%, followed by the Shield Brothers with 14%, and S.A.B.E.R 2 and Restorative Mind joint 3rd with 7%. Will the rankings change within time? Who knows!
Edit 2: From the looks of things, it seems that Darkblade has officially won this tournament! I will soon be posting a poll on best vanilla Destiny bosses, so stay tuned!