League of Legends (LoL) Question: Best Sustaining Jungler

If you mean actual sustain, as in health gain, probably Warwick or Fiddlesticks, but if they're stunned, they can still drop pretty quick.

If you're just asking which jungler can take the most punishment in a team fight, I'd say one of the big tanks like Maokai or Sion. They're not played in the jungle as often but they're still competent junglers.

If you just want a solid jungle tank, try Zac, Rammus or Gragas.

xin zhao master yi and mundo are pretty stupid when it comes to sustain in teamfights