Hardest FORCE endgame? (opinions)

Which in your orinion is the hardest endgame in chess?

Maybe the NNk vs KP?

 BBK vs KN?

Or maybe a something else?

When i said FORCE i mean in general catigory and no a extraordinary possision...

both of them is no in all possision win.

In KNN vs KP is possiple braw if the pawn is too average or by 50 moves rule draw ok salemate or lose K, And the BBK ns KN is (no some color bishop) is theoritical win if is not draw by 50 move rule or stalemate and cupture B... 

From this 2 i believe that hardest is the BBK vs KN. The other is well knows a long time ago and the 2nd a few year with endgame tablebase... 

I am waiting your opinion

Ask an endgame tablebase. 

damn straight

BNK vs K, that's hard for most people sub 1600 and is a forced win.

It's nothing on KQ vs KR or either of the ones mentioned above though.

It's pretty hard for most people super 1600 too, champ. 

K+Q vs K+2Bs (win for white, white vs black here) is borderline impossible for me, i have done some indepedent work on it, and honestly i don't understand most of the moves, and the key distinctions between the right and wrong moves half of the time.

In 1992 FIDE abolished ALL exceptions to the 50 move rule, so all of the really long, involved "forced mates"  are history; Karpov stated that was fine by him and he was talking about some of the "common" exceptions to the 50 move rule such as K+R+B vs K+R which no one knows anyway, according to Karpov. Another exception: Contrary to the opinion of almost all carbon-based chess playing units, including GMs, IBMs Deep Blue discovered K+Q beats 2 minor pieces at least 90% of the time - but it can take +50 moves. AND K+2B loses by a few more percentage pts than K+2Ns, again an unexpected finding. 

I believe it can take up to 66 moves to mate with K+2 Kts vs K+P, but nobody knows that one either; Nimzovitch was one of several GMs who couldn't do it OTB.

I can mate with K+B+N vs K but I've tried mating with K+3 Kt vs K (a "basic checkmate" in BCE) and couldn't do it.