Be good? Nah, in all seriousness if you're having trouble with the achievement wait until there's a high player count all vs. all ranked double exp weekend - You'll be able to earn your achievement easily in that. 
 
I just realised I've had this achievement for ages now:

   

Overkill Killed 4 enemies within 4 seconds of one another in a ranked free for all playlist.

5  Acquired 15/10/2007

It's generally about being in the right place at the right time. I got mine when my three opponents were fighting in a low open section of Pit Stop. I happened to be on an area above, had an energy sword, and got really, really lucky.

kill four people in quick succession.

It's actually extremely hard, energy sword/shogtun + BR and a few well placed frags should do it though. Probably easiest on Epilogue where you have the extremely tight corners, drops down and at the same time extremely long lines of sight + grenade friendliness

If you get into a swords game it is pretty easy. Just go the center of the map and use the melee attack instead of lunging. You'll beat most low levels SO easily.

Spawn kill during a game of Grifball, which happens to be this weekend's featured playlist. 
 
It's a tough achievement, but not completely ridiculous.

" @Sir_Ragnarok: That wouldn't get you the Overkill achievement. The medal sure, not the achievement.  "

Once you get good, it really should just be a matter of time. I know that's not too helpful, so I'll try to offer some tips. Grenades are a great way of killing a couple people at once. Usually when you got two people close together trying to shoot each other, you can just toss a grenade their way and take the pleasure of taking two of them. Or hey, if there's a crowd, maybe three or four. Doing that while being equipped with a one-hit-kill weapon like the rocket launcher, a sword, the hammer, or a sniper rifle can allow you to quickly add to the number. Sticking a dude with a plasma grenade can cause him to kill someone else when he explodes. Don't forget the effectiveness of assassinations, which can be done quickly and without using any ammo. Oh, also, I don't know if they do this in a ranked FFA playlist since I haven't played Halo 3 online in a long time, but if you get an opportunity to play SWAT, go for it. If you got good aim, that may be your best shot at getting the achievement.

I think the best advice is probably don't even try.  Just play Lonewolves and you should get it eventually.  If you're actually trying to get an overkill it's almost impossible.  I get one every once in a while by just playing the game.  
 
Also King of the Hill is a good gametype for multiple kills.  Don't veto if a KOTH gametype comes up.

" I think the best advice is probably don't even try.  Just play Lonewolves and you should get it eventually.  If you're actually trying to get an overkill it's almost impossible.  I get one every once in a while by just playing the game.    Also King of the Hill is a good gametype for multiple kills.  Don't veto if a KOTH gametype comes up. "

" @ArchScabby said:

" I think the best advice is probably don't even try.  Just play Lonewolves and you should get it eventually.  If you're actually trying to get an overkill it's almost impossible.  I get one every once in a while by just playing the game.    Also King of the Hill is a good gametype for multiple kills.  Don't veto if a KOTH gametype comes up. "

No. You could just end up getting to an extremely high level and then you are basically doomed forever. I'm a 45 in Lw, and there there is NO chance whatsoever of an overkill. "

" @crunchUK said:

" @ArchScabby said:

" I think the best advice is probably don't even try.  Just play Lonewolves and you should get it eventually.  If you're actually trying to get an overkill it's almost impossible.  I get one every once in a while by just playing the game.    Also King of the Hill is a good gametype for multiple kills.  Don't veto if a KOTH gametype comes up. "

No. You could just end up getting to an extremely high level and then you are basically doomed forever. I'm a 45 in Lw, and there there is NO chance whatsoever of an overkill. "

Well you're trying to kill all the people you see in lone wolves anyway, so how do you not focus on getting an overkill all the time just by playing? "

camping with shotgun/sniper will not get you overkill. Simple as that "

Don't do Lone Wolves.  Play a team playlist that uses a lot of strange gametypes.  I personally got mine on Action Sack while playing a game of Mayan Grifball.  I just swung a gravity hammer into a group of the other team and came up with the achievement.

It's mostly luck, but you can certainly put yourself in a better position to get it.

"

Don't do Lone Wolves.  Play a team playlist that uses a lot of strange gametypes.  I personally got mine on Action Sack while playing a game of Mayan Grifball.  I just swung a gravity hammer into a group of the other team and came up with the achievement.

It's mostly luck, but you can certainly put yourself in a better position to get it.

"

" @ImperiousRix said:

"

Don't do Lone Wolves.  Play a team playlist that uses a lot of strange gametypes.  I personally got mine on Action Sack while playing a game of Mayan Grifball.  I just swung a gravity hammer into a group of the other team and came up with the achievement.

It's mostly luck, but you can certainly put yourself in a better position to get it.

"

It has to be Lone Wolves. "

" @ArchScabby said:

" @ImperiousRix said:

"

Don't do Lone Wolves.  Play a team playlist that uses a lot of strange gametypes.  I personally got mine on Action Sack while playing a game of Mayan Grifball.  I just swung a gravity hammer into a group of the other team and came up with the achievement.

It's mostly luck, but you can certainly put yourself in a better position to get it.

"

It has to be Lone Wolves. "

Overkill
Killed 4 enemies within 4 seconds of one another in a ranked free for all playlist.  I don't see it saying Lone Wolves on this. "

I could be wrong, but I'm pretty sure you definitely have to get the overkill achievement in Lone Wolves. I got it on guardian with a shotgun, you really just have to play a lot of Lone Wolves and eventually you'll just get lucky as long as you aren't horrible at Halo. That's my advice to you.  
 
If you're really desperate, get a few friends together and go into your settings on your Xbox and change your language to something obscure. Then when you're in Match Making change you're preferences by pressing X in the lobby to same Language. Then you'll get matched up with you're friends and you can set it up so they let you kill them for the achievement. 
 
Good Luck.

" I could be wrong, but I'm pretty sure you definitely have to get the overkill achievement in Lone Wolves.  "

I really don't like multiplayer  achievements in game like this . It encoruges people to play differntly to how they noramlly would . Like on Gears of war 1

" I really don't like multiplayer  achievements in game like this . It encoruges people to play differntly to how they noramlly would . Like on Gears of war 1 "

i did it by playing king of the hill on the pit and waiting till the hill was in sight of one of the mounted turrets and just fired at the people madly fighting for control

Set language to Italian.
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Ask them if they want to "speak Italian".
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