Hollyleaf is not evil
Oliveleaf Hollyleaf is not evil. She may have done a few wrong things, but her purposes were not evil.She killed Ashfur. I know that seemed really evil of her, but it was for the good of everyone else. Hollyleaf was protecting a secret, a very dangerous one. Squirrelflight and Brambleclaw were not her parents, and if Ashfur told everyone, they could have been killed. Hollyleaf didn't know who her real parents were at that time, so she needed to kill Ashfur so that the other cats wouldn't think her parents were rogues.
Then she forced Leafpool to eat deathberries. She bad a reason for that also. She is a very emotional cat, so when everyone hated her, she needed ro blame it on Leafpool. Leafpool was the cat who caused all the problems: from breaking rhe warrior code to creating a big lie. Hollyleaf may have overreacted a little when she lashed out at Leafpool, but I don't blame her.
Besides the "evil" things she done, she also did good things. For example, she saved two apprentices from a fox, and even died saving Ivypool from Hawkfrost. She is a very loyal warrior, and therefore does not deserve being called evil.