Harry himself admits that Susan would have lived if he had thought things through. for instance, if he had seen the red king's betrayal coming then he could have forced him to actually honor the deal and they all would have left with the girl.

He gets a pass on killing Susan because he didn't use magic to kill her and didn't do any of the actual magic involved in the spell, so it's not technically black magic, and while it might be skirting the edges of what a wizard can do the results and Harrys support among the younger Wardens mean he gets a pass from them. Technically it was murder, and it was a nasty, grubby deed, but it wasn't premeditated. Until he and Susan were in the room he had no idea what was actually going down, and if you can see another way out of the situation he was in when he made the decision to tell Susan who kidnapped her daughter that didn't involve everyone he brought with him dying you are a smarter man than I. He could have seen it coming if he had a bit more information or was a bit smarter, but he wasn't. And they aren't so much giving him a pass as not bringing it up. He already literally sold his soul to get there, and they know he really didn't take it well, and he had already subconsciously decided to kill himself before he even did it, which at least one person knew, and more than one other had probably had a pretty good idea he was going to given what they said to him in hindsight. Plus, technically he is dead so no one has had much time to yell at him about it. I'll be surprised if it doesn't come up in the next book, frankly.