There is a MP emblem to get 10 combo kills in legends, but I don't know what they mean by combo kill. Any ideas?

If you kill 2 enemies fast you get double kill. If you kill three of them fast after each other you get tripple.. etc.
Basically you gotta get 10 quick kills... I think.. not sure
or maybe 10x double/tripple/ multi kill

I don't think so. I saw "combo kill" displayed once, but I don't know what was particular about the kill. The 2x 3x ... kills happen often, so I should already have the emblem. Maybe it is a kill somehow done by both players simultaneously?