Complex sentence: Tanya could be considered to be the single most untrustworthy character in the series: she betrays Liu Kang in her "Mortal Kombat 4" ending, plus her entire home realm of Edenia as well as fellow residents Sindel, Jade and Kitana.
Split into simpler sentences: Tanya could be considered to be the single most untrustworthy character in the series. She has betrayed her entire home realm of Edenia, and important key characters in the realm such as Sindel, Jade and Kitana.