The Loyalty skill intrigues me, because it must be a mistranslation. Maybe it means "Loyalty to whoever is the boss at the time". In fact, everyone who has the skill naturally was a traitor at some point!
Cai Mao - Plotted to take over after Liu Biao's death, and served Cao Cao.
Cao Bao - Turned against Liu Bei after being beat up by Zhang Fei.
Han Song - Servant of Liu Biao,urged Liu Cong to surrender to Cao Cao.
Hou Cheng - Betrayed Lu Bu.
Liu Feng - Stranded Guan Yu and did not send reinforcements to Jing.
Meng Da - Surrendered to Wei, then attempted to rejoin Shu.
Mi Fang - Betrayed Guan Yu and joined Wu.
Yang Qiu - Surrendered to Cao Cao after the defeat of Ma Chao's riders.
Yang Song - Sold out Zhang Lu, famously corrupt.
Yuan Shang - Turned against his brothers and fought amongst them while Cao Cao sought control of their father's lands.
Zhang Ying - Was killed by Sun Ce's men after boasting he could beat them. I guess his badness was kind of a betrayal too
Zhang Yun - Was part of Cai Mao's cabal to usurp Liu Cong.