I moved out of the unit in January as I found someone to rent and in the first month of the new tenant living there they too filed a complaint against the below tenant as they heard verbally abusive behavior as well.

Understanding behavioral tendencies will take you further personally.

Originally posted by @Robert Hernandez:Talk to the neighbors and see if you can't work together to discourage the behavior.

Past behavior is an indicator of future behavior, so I would categorize anyone with bankruptcy or housing court on their background as higher risk. 

If not, seriously consider it, as this will cut down on the cat behavior of "marking" their territory.Find out what the carpet stains are and attempt to remove them.

He seemed to change his tune when he saw me evict 2 of his neighbors over their behavior, yet I still allowed him to sign a 12-month lease, in spite of his negative behavior up until now.

People are on their best behavior before they get the keys.

It is not expected that pets are going to pee and poop on your floors and I would advise that you not just accept that behavior just because you accept pets.  

Tenants behavior is escalating and I found out by a bit of sleuthing  that tenant did not allow the previous LL entry after requesting a list of repairs and was a complete terror.  

is it a civil matter ( small claims) or can the city line like a code violation.I bet tomorrow you will see 1000 landlords in pioneer square demonstrating breaking windows and doing all manner of dectructive behavior