Seriously 343i? Get the most random medal in a game type that’s also totally random?
If there actually is any strategy to getting this medal, it’s to feed the other team kills and let them win. Try to ensure all four opponents are on killstreaks to give yourself the best chance of killing one of them before your teammates. Yeah, real great gameplay 
And why does this have to be in Fiesta? I don’t like playing it, and this challenge requires circumstances you can’t control (unless you sabotage your own team), meaning you may have to play it many, many times to achieve.
I can’t even swap out the challenge for some reason, and I already burned a bunch of swaps to avoid playing FFA and other challenges that are very random.