Hey guys, Just popped this and managed to capture it on the xbox one DVR.
How to get SOLOObviously the best way to get this achievement is by using hanzo's special on groups of enemies on tight areas of the map or even better tight areas that have an objective close by.
Don't get nervous and use it straight away or at the incorrect time, But do take some chances early on in the rounds, as you will get your special back quick enough.
A good tip: Use hanzo's recon arrow to highlight any enemies that may be close by. That way you can time your special for when they turn the corner.
Previously I had been getting around 3 kills most of the time. Patience and good timing is key.
Please note: I am also firing my arrows at the same time but I couldn't have killed anyone with them as the achievement popped straight away.
The video but captured via the xbox one DVR, So you will not see the achievement pop but it did.