I always kinda felt bad for Leopardstar. In this rant I'll explain why she not to blame in my opinion.
Rant 1: "She let Tigerstar kill her loyal deputy,Stonefur,because she was in love with Tigerstar and wanted him to love her."
First of all I don't think it said in the books that she was in "love" with Tigerstar.Even if she was he wouldn't love her back (being Tigerstar and all :3). With the tigerclan incident, Tigerstar made it clear that anycat who dared disobey him would die a slow painful death. Plus even if she died Riverclan would be left without a leader and would be left with Tigerstar as a leader. I believe that she guilty about stonefurs death and didn't want to let her pride get in the way of her judgement ever again.
"She realized her mistake when Tigerstar combined their clans into Tigerclan and made himself leader, then made the half- clans fight to the death. Whatever leopardstar hoped for,this was not it.But she was trapped by her pride and couldn't speak out against Tigerstar - not because she was scared for her own safety, but because she couldn't face losing the respect of her clanmates by admitting she was wrong."
Plus leopardstar saved her clanmates by agreeing to join lionclan with firestar. If she truly was bad she could have declined his offer and many more lives would have been lost.
"If she seems hostile and defensive when dealing with other clans, it's not because she doesn't trust them; it's because she no longer trusts her own judgement."
One last reason is that she regretted it as seen in Mistystars Omen :
"I never deserved your forgiveness" Leopardstar whispered.
Plus she expected Mistystar to hold a grudge and want revenge though she doesn't (because Mistystar= pure awesomeness):
"But I don't want to lose you!" Mistystar protested.
"Really?" Leopardstar wheezed. "Even after what I did to your brother? All the Half-clan cats? Mistystars Omen, chapter one.
These are some of my reasons why she deserves less hate.

Update: comment which cats you'd like me to do next!! And if no one comment i'll not continue it