For this achievement, you need to get gold in all the cups..you dont necesarily need gold in all events, a few silvers is ok, aslong as you reach the required number for winning the total cup...on the mainpage, it will show you how many points you need for gold, silver and bronze respectively.
when you start this playmode, dont focus too much on gold...just finish the first event, and keep redoing the first elemination race, until you earned enough Money to upgrade your weapons and your first vehicle (i suggest the supercar, if you finished the storymode first, and when you get the militarytruck after reaching silver in the third cup, you should max upgrade that one also...
if you find yourself having a hard time getting gold in the first endurance and elimination events, just play through the first three events, getting silver in the last one, to unlock the military truck, which will make these events childsplay
For the endurance events, you should choose a fully upgraded military truck (gained from getting silver in the drivers event, which is the third race)
Its easier to control, as its not as fast, and huge, so you hit a lot more boxes and zombies for extra time.
Worry more about kiling and destroying stuff, while keeping a steady pace, than just speeding through.
For most events i got gold in first try, ranking top 50 on the World leaderboard using this strategy, without even trying
Use a fully upgraded military truck for this (you get it for reaching silver in the drivers event, which is the third event in the blood race playmode.
With this big monster of vehicle, you will kill most cars with one ram, while using nitro..and thats how i killed 70% of my oponents...weapons are secondary way of killing..
Also dont try to speed too much, just keep a steady pace, which will give you more kills, than just chasing number one..
these are a pain in the a¤#, especially the later ones...
they are truly random, and often see you leading the race, to then get hit 50 metres before the finishline, and ending 6/6.
i used the super car for this, which is unlucked in the storymode, in one of the last misions. But any fast car with decent armor will work for this..
expect a lot of retries on the races.