Mikan Tsumiki is an emotionally fragile and meek girl, who has very low self-esteem from years of bullying and abuse. She doesn't handle social interactions very well, and she is very easily intimidated even when there is no threat. Her constant state of self-deprecation and paranoia causes her to have aggressive outbursts which shows a side of her that is unlike how she usually is. Her outbursts involve sadistic obsessions with people, resentment for her abusers, and strange urges. 

The Ultimate Nurse, Mikan Tsumiki

Junko Enoshima is a very intelligent, cunning, manipulative, cruel, and toxic person. She lives off of the sadness and hopelessness of others, and she feels absolutely nothing about doing horrible things to innocent people. Junko loves playing mind games and toying with emotions, and it's very hard to tell what she really feels in any situation. At times, her personality can change on a whim during conversation. 