I think KQ or KJ can often be a nightmare. You are in no man's land if anyone raises (let alone re-raises) but you have to play them.
In terms of hands I genuinely groan about - it has to be middling suited connectors such as 8 9 of hearts. Obviously, in broadening any range this is the type of hand you should enter pots with. All I can say is I wish this was a stat I had bother to keep because with middling pairs I can barely recall times when such cards have paid off.
Middling suited connectors so frequently fail (for me) that for sometime I have stuck to suited broadways, this said, see above!