UPDATE: CrashingPanda from x360a.org confirmed that this could be done ALONE in training ground. You'd need the Animus Hack and Poison abilities. The bonuses that count towards Greater Variety are:
- Hidden Kill
- Acrobatic Kill
- Poison Kill
- Animus Hack
- Streak Bonus (set up a kill streak bonus that gives to a bonus for five consecutive kills)
I'll test the above later to recofirm.
Meanwhile, below is my previous solution, which obviously still works and would make things easier if you've two persons.
This achievement can be unlocked in Training Ground with two players in private.
Set it up as follow:
- Private on Extra Content Maps
- Training Ground
- Map: Florence (i.e., Firenze)
Invite your friend into the game before launching. Otherwise the game will begin as soon as you launch because training can be done with one person.
Make sure you have at least the Poison ability. Templar Vision would be nice to spot targets in morphed/ blended crowds, but isn't really necessary.
In training, both your buddy and you would be killing. There's no time limit. Take turns doing the following. The following can be done in any sequence.
1. If the target is blended in a stationary crowd, lock onto him/ her, and blend into the same crowd. Wait until your approach meter is Incognito and when your focus meter (the circle on the "X" that's on the target) is fully filled, and perform the kill.
You'll get the following bonuses:
- Hidden Kill
2. Perform the following kills next on the subsequent targets:
- Silent (the approach meter is above "Discreet", is showing "Silent", and has not fully filled up to "Incognito")
- Discreet (the approach meter is showing "Discreet")
- Reckless (get close to a target when discreet, then run up and perform the kill - the meter will change to "Reckless" when you start running)
You'll get "Variety" by the 5th bonus you do.
3. When doing "Silent" or "Discreet" above, get close enough to your target and perform a Poison kill. You'll get:
You can also do this on another target separately from the above if you aren't confident of doing a few things at the same time.
4. Perform the next kill on a target that is near a building. If he/ she isn't, kill and move on until one appears near a building.
Lock on to him/ her, hang on the ledge above, and kill. You'll get:
- Acrobatic Kill
5. Lock on to the next target, and get your buddy to kill him/ her. When the target dies, immediately run up and kick him/ her. You'll get:
- Ground Finish
- Greater Variety
The achievement should unlock now.
Alternatively, you could do 1-vs-1 in Manhunt, doing a few of the above actions when you kill (there won't be enough time to do everything, and you won't be able to get easy ones like "Assist" and "Ground Finish"), and adding the following bonus when you hide:
- Escape (get your friend to trigger a chase, then hide)
- Brutal Escape (trigger another chase, then stun your friend)
- Lure (you need the "Blender" perk or the "Morph" ability - get into a crowd and then morph it so as it turns into a crowd of your character. Get your friend to kill the wrong person)
Hope these help. If there are any other bonuses I missed out, please comment.
PS: Personally I did it with 2 other friends in 2-vs-1. We added "Assisted Stun" to the fold for one of them as well, but all the above actions have been tested to work in our session. I've also tested Training Ground.