Re: the Double Trouble achievement where you have to take down the same Revenge Rival in a single event (think Burnout Revenge) I came across a discovery by accident.
This is actually very doable since many people haven't really understood the word 'event' including myself.
This achieve does not mean you have to do this against the bot-cars in a single race. I was dreading this achieve thinking it was actually going to be the hardest one of the 1000. How could you get a bot-car to nail you *twice* in a race? AND get them back within the minutes allowed? Etc.
All you do is load up your favourite "event" (i.e., Race, Map...) (not an Elimination race, but another one you like) and just play it again a few times. This achieve pops when you have gotten revenge (twice) on a single, particular bot-car for that particular "event-name".
If you've played Burnout Revenge, it is exactly the same thing. Namely; the data is stored on who you actually took down (as well as logging that data for that particular event-name you just played). As long as you take down that same bot-car again within the same event-name you've got it.
This only took me 3 races to nail this achieve.
In a nutshell, you don't have to worry at all about the impossibility of getting a car to nail you twice in one race, and then getting him back 2 times in the same race.
Hope this helps anyone else who might've misunderstood this achieve like I did. After getting this, the rest of the achieves are very doable.
UPDATE/EDIT: Also I should mention that this cannot be onlocked in Multiplayer.