Continuing with the "One/Multitude" theme we started with 八面六臂, let's take a look at another yoji that describes one person taking on a considerable amount of work, albeit in a slightly different vein.
1. Strong enough or skilled enough to take on an army.
2. Being extremely formidable in your field.
There are actually a number of other 四字熟語 that have the same meaning, so if you think you might be able to use this one, consider varying it up with yojis like 一人当千（いちにんとうせん）、蓋世不抜（かいせいふばつ）, or 万夫不当（ばんぷふとう）. But don't expect the average person to recognize all of them, necessarily. From what I can tell, 蓋世不抜 is pretty rare, and 一人当千 seems most common, but not most correct. A google search for it will bring up about 6 million results, but it will also bring up the "もしかして：" prompt which will ask you if maybe you meant... you guessed it, 一騎当千.
Also, I like to think of these alongside the family of 天下無〇 yojis that Brett posted on forever ago.
See what you can do with it.
(NOTE: One thing that you SHOULDN'T DO with it is a Google Image Search, on account of it seems to be the name of a manga that is either naturally pornographic, or lends itself to pornography of the 同人誌 variety.
アンドさん： それは確かにそうだよ。。。。 ペンペン。