About Greystripe, you seem to dismiss the fact that he's potentially one of the most tragic figures in WC; he lost his mentor right in the first book, then falls in love with Silverstream who dies from childbirth, then one of his two kits dies in the following arc, he finds someone to love again only for her to get sick and die in POV, then one of three kits he had from her loses the use of her hinder legs and, you guess it, dies the arc after that. Honestly, his life has been a mess :<
Also, his choice to leave Thunderclan for his first two kits is understandable since he cinsider himself responsible for the death of their mother and wants to fix that somehow. Again, it might've been stupid in the longrun, but in that moment it made sense...
His life is certainly a mess, and it's his fault. He didn't have to fuck Silverstream after refusing to break up with her, get her pregnant and then presumably have her come over the border for the sole purpose of being there with her when the babies came, which couldn't have helped her chances of survival (there's literally no other reason she'd be there at the time). He didn't have to break the law, eat prey he should be giving to his Clan and then attack Fireheart whose only crime was trying to get him to stop breaking the fucking law (which he never apologizes for, by the way). He didn't have to sit around in the already busy nursery, staring silently at his kits instead of helping feed the queen caring for them. He didn't have to ditch the Clan for kids he had no rights to, prove to be an extremely useless RiverClanner, and then betray his new Clan (who took him in despite their [admittedly incorrect] belief that he was responsible for the death of one of their own), getting kicked out afterwards. He didn't have to promise to help Squirrelflight, immediately break the promise and abandon his Clan for no reason and for the second time in his history. Hell, he didn't have to join in on the final part of ALITM and get his stupid ass killed by ghosts because he's an old man who shouldn't be fighting anymore.
But he did all that, didn't he? No one told him to do any of those things. Those were all his decisions. I find no reason to be sorry for him when he's the cause behind damn near all of the things that happen to him.
And here's a reminder that every single character in this series goes through hell. Greystripe is not a special case. He's highlighted in the eyes of the fandom because he's a main character, and that's it. The difference is that he's had a hand in a lot of what went wrong in his life, whereas many, many other characters were innocent victims (for example, like you said, his own daughter) and were still better people than he is. The writers treat him like he's a grand hero and a good friend and a wonderful person, when their actual story, especially in the first arc, painted him as nothing but an incompetent scumbag.
There is a massive misinterpretation of his character that's widespread through this fandom and I fucking hate it. Greystripe was not a good person in the first arc, and the fact that his faults were never once acknowledged and he never grew or apologized pisses me off to this day.