Here is what I would do (without seeing the picture it goes with is hard to guess):
I'd emphasize the ambiences before he jumps down or out of or from wherever he is, then fade to zero before he hits the ground.
Then use a regular-old oscillator starting about 80 Hz and sweep it down to 25 (depending on what it will be played back on, add a DBX 120A, compress it maybe) as well as using a monotone element like bowed glass or something shrill and that has high-frequency content and pitch it using the same envelope, and then I'd try something cool like modem noise or 8-bit distortion or something really low-fi might sound great there. Or try turning the previous sine-wave into a saw-tooth or square wave and filter it and do crazy stuff like on one of those Korg mini-keyboard synths. Might be awesome.
The reference I'm thinking of for you to check out is in the Prologue to Lord of the Rings - Fellowship, when Sauron gets killed by the King and it fades to zero and theres just a low sine-wave blaring like a sonic boom.
But, things like this it's best to experiment and as you experiment you'll ditch previous ideas and go with new ones now acquired and just have fun - that's what designing sounds is all about.
P.S. don't forget to post what you end up with! Good luck!