Forza Motorsport 5

just simply create a private race between yourself and the AI and as the description states come in last place and you will get this once the race finishes

Let's be honest here this will be the easiest 0 gamer points you will probably get. So what you could do is just make a private match against AI and lose to get the achievement but what's the fun in that? The way I almost got this achievement was I truly sucked, but in someone's last ditch effort to be a douche right before the finish line he tried to cut me off for fun. Needless to say I flipped his car and I took second to last. So my recommendation is to go all out. Take that last place glory with you're head held high. Join a match with legit players but take your time in the race. Sit down with some milk and cookies as you make your way through the track. Enjoy the scenery. Possibly try to cut off the person in first place as he is about to lap you. But the best of all is have fun!

Note* - You have to actually finish and cross the finish line in order to unlock this achievement. If the time runs out and you do not cross the line then this will not unlock.

As Private race appears to be having issues, i have found the quickest way to get this achievement is to go into multiplayer - drag racing. You dont even have to change your usual car just be a second or two slow off the line. This is even easier if you have the two car race as an option when voting for match settings. Just make sure you finish last!