Kaikeyi plays a similar role to that of Judas Iscariot in the Bible's book of Luke. Both parties betray the "chosen one" of the religious narrative, yet without their treason, neither Rama or Jesus would have been able to fulfil their foreordination.
Kaikeyi was convinced by the hunchbacked servant Manthara that following Rama's coronation the king Dasaratha would throw her family aside and that she felt she had no choice but to rid the city of Rama. In Luke 22, it is stated that "3 Then Satan entered Judas, called Iscariot, one of the Twelve". In both cases, something overcame the betrayer into committing their offence to their protagonist. However, Judas' turning point can definitely be seen as more two dimensional and vague. We can not tell if his "possession" was a mental dilemma as well or if it was a literal possession by satan that drove him to betray Jesus. Kaikeyi's decision definitely seemed more humanistic and relatable and dwells in more of a grey area than the blatant statement of Judas' posession.
Without the betrayal by Kaikeyi, Rama would not have ventured out into the forest, and in turn would not have killed Ravana just as without that of Judas, Jesus would not have been crucified and therefore the gates of heaven would not have been opened. While they are regarded as villains in the texts, they are both necessary evils without whom "the chosen ones" would have failed their destined paths. This raises the questions; if Kaikeyi hadn't been convinced that Rama's ascension to the throne would be her doom, and if she had still supported Rama as King, would Ravana still have died and would Rama have accomplished less or maybe more spiritually? If Judas hadn't betrayed Jesus, would Jesus still have opened the gates to heaven? If not, then did Satan not play a part in helping to open the gates of heaven? Were these characters destined to be evil, or did they have the free will to decide? Or ultimately, if they were to be "good", would it have really have been good for anyone?