fwiw PASOK-DIMAR and Potami both may be replaced with a centre-left new party, probably led by Athens Mayor Giorgos Kaminis.
KKE (Communist Party of Greece) would receive my vote since, although I agree more with Popular Unity's platform, the latter is unlikely to gain seats in the Hellenic Parliament. The KKE is a solid left-wing party that will likely win a couple dozen seats so, strategically speaking, it'd be wiser to vote for them to advance a left-wing agenda.
the KKE are very, err, cult-like. They have no interest in participating in government, which make them more of a burden for the left than anything else.