On urban maps it's even easier.
Manhattan Bridge, Hagental Base, even Cairo and Gibraltar actually empower infantry greatly as there are no/less vehicles to worry about, I'd argue these maps are even easier to achieve high amounts of kills in.
I got multiple 50+ kill matches yesterday.
Deaths will entirely depend upon the player's team, typically though, as being downed doesn't actually count as a kill, only bleeding out/giving up does. Play style also factors into this, obviously someone ratting or sniping will die than someone pushing objectives.
Sometimes I'll go 60 kills with deaths lower than 10, sometimes 40 kills with like 12 kills.
