Brawlhalla

This achievement can be tricky to do legitimately, but there's a few ways to tackle it. First, I'd recommend going for this in Friendly 2v2s because you are more likely to face a team that is easier to beat. Both enemy players have 3 lives each, so you need to get every KO on both of them in order to earn 6 in one match. The first way to go for this, which is probably the trickiest and least reliable way to do it, is simply play 2v2 games with a random teammate. Since you only need the kills, let them do damage to the opponents before moving in to KO them. This is tricky because you have no control over your teammate, so if they get a single KO, you can't get the achievement during that game. With some patience and luck, it is doable this way. The second method is to find a teammate and play 2v2s with them on your team, either locally or online. This way you can have a teammate doing damage to the opponents as well as taking hits from them while you attack. It is not flawless, since your teammate can still get KOs by accident, but it is a lot less likely, and since you are communicating, you will likely do better than you would with a random. The third method requires you to either get very lucky with your opponents or be good at the game, as well as a second controller. Play 2v2s with a second controller locally and have it AFK, then face both opponents on your own. This may sound daunting, but it doable as well. If you get an opposing team that has an AFK second player or one that doesn't know how to play, you only have to beat one player to get all 6 KOs. This is how I managed to get this achievement, but not everyone will be able to pull it off.

I would recommend trying to find a partner to play 2v2s with, because this is the easiest way for you to get this achievement without being really good at the game. Without boosting though, you will likely have to be at least decent at the game in order to get this achievement in general.