Also see: How to find a good confessor
To avoid a bad confessor, avoid the priest who…
… is merely a lionness instead of a lion in the pulpit, and who, instead of being a lamb in the confessional, eats the pentitents who come to him for mercy.
… mocks penitents. This is a crime that cries to heaven for vengence.
… talks about confessions, whether directly or indirectly. This is a crime that cries to heaven for vengence.
… does not offer scheduled confessions, though such would be very possible.
… makes if virtually impossible to schedule a confession, though such would be very possible.
… does not preach up going to confession.
… discourages confession by telling people the only ones he wants going to confession are rapists, pedophiles and murderers, so that, predictably, no one lines up for confession (and this does happen…)
… offers general absolution without the permission of the bishop and with no catastrophe at hand. By the way, large numbers of penitents do not a catastrophe make.
… tells people to confess only one sin, which may make their confessions non-integral and therefore sacrilegious.
… mocks the desire of penitents to have a screen partition. (Note that some priests want this screen, but the pastor, who has the say over building projects, will not permit it).
… is otherwise careless with the Sacred Liturgy, and who dissents from Church doctrine and morals. He will likely just confirm you in your sin. Is that what you want?
… asks solicitous questions about you which he has no business asking, which have nothing to do with what you’ve confessed, such as details about where you live, etc.
… who, at a penance service with individual confessions, publically gives everyone the same penance, such as saying the Lord’s Prayer, the Our Father, once, before the confessions even begin (or after). This is a terrible disservice to the pentitents, who are to have their penances tailored to their confessions.
I could go on, but you get the idea. See How to find a good confessor.