I might be a bit on the wrong here so, feel free to correct me if you think otherwise but I think Tsleeixth's virtue is Patience while his Sin would be Wrath (not in the sense that Tslee is constantly angry but, more like, he is easily enraged by things such as the mistreatment the Argonians recover at the hands of the Nords or by the invasion of the Kamals and what they are doing but it's sort of a more subdued kind of wrath)