Bad Luck

Is there some specific placement in chart that indicates bad luck?

bad placements to Jupiter maybe....

what kind of bad luck?

Jupiter can bring the good stuff even squaring or opposing something, the danger here is the excess (Athina Onassis, very rich, very fat, plenty of rich food etc)
Generally any Jupiter contact is ok
There are some placements that can get you into trouble, but they're too many to count and they do require your participation and poor judgement, too