Neither is zoro, also zoro could've refused to kill him, he could've just knocked him out since Mr 7 was probably pretty weak, but he didn't, as zoro says it himself, he follows a path of carnage so yeah killing is something he actually wants to do
I don't know where people got the idea that zoro is good, he's not lol, far from it he is an anti hero, where as luffy sanji and Nami, chopper etc... are genuinely good, luffy and sanji more than the rest for dozens of reasons
Zoro actually likes beating the crap out of people and killing them, he's been called out for it a few times, at Fishmen Island usopp said he didn't have to be so violent when fighting neptune and that they aren't evil pirates, and in the Manga he killed the dog that was gonna attack that little girl, he could've just threw it away, the guy can outrun bullets, but he chose to do something Because that's who zoro is, he's ruthless
Zoro is a necessary evil, I hope people realize that in his second flashback, he repeatedly stated that he is not a good guy, he just follows luffy out of respect, but if luffy did something that zoro does not respect, like forgiving usopp easily, he would just leave