You can sue him for breach of contract, although that doesn't allow you to recover for mental anguish. It would allow you to recover your security deposits and possibly some of the rent you paid.
I'm not sure from your facts as to whether he evicted you or you left voluntarily but if you left voluntarily you could also sue for "constructive eviction" which means he made living conditions so unbearable that it was equivalent to him evicting you.
If he failed to properly handle the security deposit issue you could sue for that as well. That would be a lawsuit for breach of contract as well as a violation of statute. You can see the statute at http://app.leg.wa.gov/rcw/default.aspx?cite=59.18.280 but note that there was a statutory change in 2016 so if you started living there and put your deposits up in 2015 you woudl want to sue him for that statute as well as this one: http://lawfilesext.leg.wa.gov/biennium/2015-16/Pdf/Bills/Session%20Laws/Senate/6413.SL.pdf
which is the new one.
Likely the old statute is the one that will apply. If you read through it at the link above it gives you specifics as to how he was supposed to handle the deposit.
In Washington state the small claims court (which you can read about at https://www.courts.wa.gov/newsinfo/resources/?altMenu=smal&fa=newsinfo_jury.Scc) only has jurisdiction up to $5000 so if you want to sue for more than that you need to do so in one of the higher courts and you will likely need a lawyer. However, you can sue for your attorney's fees as well.
Any of these causes of action will get you to any of the damages except mental anguish. You could argue a trespass by the landlord, although that is a little difficult to prove since he is the landlord, and that cause of action would allow you to get mental anguish damages.
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