Easy to get achievement in event/ operation "daily bugle and midtown patrol (as tmw666 pointed out). Any difficulty will do. To get it quick I suggest going with the lowest. At first you have to disarm 3 bombs then move on to the next part where the 1st villain will wait. Defeat him then move on defeat 2 more and one last on the roof of daily bugle. Appearing villains (Though not all of them) will change every walkthrough. Got the last 2 on my 3rd run.
You will have to defeat 10 different villains of the following ones ( Iwill add them if you find more. Just leave a comment)
*** Spoiler - click to reveal ***Doctor Octopus
Grim Reaper
Rhino
Shocker
Lizard
Vulture
Kraven the Hunter
Venom
Tombstone
Green Goblin
Electro ( Spezial Thx to Darklights for adding him)
tmw666 pointed out that villains from the sinister six will also count from defeating them in midtown patrol. (special thx to you as well helping to improve the solution)
According to Fummm Showdowns along the story path count as well. Thx for trying and confirming.