The most common complaint of Heart of Swarm is the poor writing which abandons the momentum of Wings of Liberty in favour of Kerrigan's personal revenge story.

This is most apparent from Kerrigan's characterization. Kerrigan undoes all the hard work of the man she loves by transforming back into a Zerg to get the power to take down Mengsk. This time it’s different though because she apparently has full control of herself as opposed to before where she was under Amon's influence.

However, it doesn't seem like she has control of herself as she constantly flip-flops between good and bad. She genocides billions of people across numerous planets, but the other characters keep giving her a pass because of her token moments of morality where she reluctantly spares the lives of people who did nothing to her. Somehow, she could kill trusted generals and threaten the lives of their leaders, but she faces absolutely no repercussions for any of her actions and everyone keeps trusting her and working with her.

This isn’t bad writing and is completely consistent with the ending of Wings of Liberty which saw her revert into a human female.