It's Peter Hale. 100% without a single doubt in my mind.
- He was robbed, a perfect way for him to look like the victim in the situation when in reality he likely hired the mouthless assassin to be the one to take it.
- He was attacked, BUT he isn't on the dead pool, at least not the two parts that are unlocked already. We saw him be initially attacked by mouthless, but we didn't see his escape. Could be likely there was a payment dispute there, but we'll never know because *gasp* Peter killed him!
- Malia isn't on the hit list so far, and while we all assume Peter doesn't know the truth about who his daughter is, he's not a moron.
- Peter is apparently gaining power while Derek is losing his... how very convenient for him.
- The Ciphers are a red herring. Likely a coping mechanism specialized to Lydia to deal with unlocking her banshee powers. Allison being the first name is there to make the audience suspect someone connected to her, but then Aiden was the second so we have two people who were very special to Lydia. The third name will probably end up being something like Jackson.
- Parrish's name on the list is a red herring too since everyone is assuming it's a list of only supernaturals, but for all we know the bottom third will have more people who aren't. People such as Sheriff Stilinski perhaps. Again, this is for the audience so we'll all obsess over what Parrish could be instead of trying to figure out who the Benefactor is.