Talon, at its core, is a terrorist organization. They want only to cause conflict and will use any means possible to reach their goals, including murder. Because of this, Talon as a whole is absolutely evil; however, if we look at agents as individuals, then the answer is not so simple. Sigma, for example, I would say is not evil, instead, he has massively misplaced ambitions that have driven him mad. Moira appears to be more immoral and uncaring than pure evil, and Widowmaker's evil is due to reconditioning that is not her fault. Doomfist, Reaper, and Sombra are likely the evilest Talon agents - while they may believe they are in the right as they pursue their goals, the damage and chaos they leave in their wake are unjustified.