The Hatfields started things and perpetuated most of it. They were a much more powerful and affluent family in the area and were well connected politically and financially, so technically, yes , the McCoys were the bigger losers. They also lost the most life and tried to do their fighting in the courtroom because it was the only power they had. While most of the men of the area were out fighting a war Devil was back home taking advantage of industry and largely profiting from it while a lot of others (not just McCoys) suffered in the area because of the war. The Hatfields thought they were the law and lived by the gun. Randall's three sons that killed Ellison were brought to justice but in the wrong manner and that made things linger. The McCoys were right to put out warrants on the Hatfields and the Supreme court agreed and upheld them. Phillips crew actually arrested 9 men, including Wall (he didn't turn himself in). They didn't do this until after they were legally deputized and the warrants issued though. Randall was outta the mix after his sons were murdered and it was Cline that continued the feud. Randall was 14 years older than Devil so he was an old man at the time most everything went down in tonight's episode and he wasn't involved in anything other than the New Years massacre. The reason why the Hatfields went to kill him is because he was the only one that could testify against them in the way the Hatfields kidnapped his sons and killed them themselves. The warrants were legit and they didn't have a leg to stand on so they did what they do and went to the guns.
Some other interesting notes...
Wall Hatfield participated in the New Years massacre and he wasn't the judge that presided over the pig case.
There was no shoot out between the two clans like they showed tonight. Randall was out of the game.
Randall and Devil didn't fight together in the civil war.
Devil didn't write a letter calling for peace. The government intervened and put an end to things to help attract the coal industry and rail industry to the area.
Sally was beaten senseless when she was attending to Allifair. She didn't come out dual wielding