An unpleasant overcall.

[Thrakkar]

the only holdings that make sense to me are:
MP: 2 clubs > Qx (he but should have raised the turn then) > Ax (he should have raised the river then)
SB: 66 or Ax (explains call PF & donk bet on flop) >> Qx (far less likely, but he might have tried to probe you on the flop and get rid of MP)

Given these holdings, you are ALWAYS beaten by SB and SOMETIMES beaten by MP (with Qx, but quite unlikely). To me this basically boils down to how likely you think SB is bluffing. 30-40 BB seems to be a good minimum.

Thomas

P.S. Why didn't you cap the flop?