I think Bg5 is considered sharpest, though you have to be prepared for Black to play the poisoned pawn variation. Bc4 is pretty sharp too, though.
The sharpest variation against the najdorf?
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the sharpest is 6.f3 ...
6.Bg5 can lead to extremely sharp variations - e.g. the Poisoned Pawn like Spiffe mentioned, but also many other extremely wild variations other than the poisoned pawn.
6.Be3 e6 7.g4!? can also be very sharp.
By reputation, 6. Bg5 is the sharpest, but 6. Be3 may be better. I have no idea - this is just based on reputation.
can someone post the poison pawn varition please?
Which system is the sharpest against the najdorf? the Bg5 f4 lines or Sozins or English attacks? Thanks!