Yeah, multiple times. Not incredibly hard to kill a boar, although I imagine without the necessary equipment on a deserted island it would be a lot harder. And the problem is you really need to stick its jugular. If you get anywhere else the boar will probably get internal bleeding and won't drain very well and will probably ruin most of your feed.
Ever had one charge you? I heard you got to stick a boar with a pretty big knife. like this
It's a pit oven. You should know that, you're kiwi after all
I've had one clip the back of my Achilles tendon, I was very lucky to only need a couple stitches. But that was the only time I've been charged at. Every other time pigging dogs have done most of the work with me only needing to stick them at the end. And yes the knife has to be pretty big and strong. The jugular is very thick to cut through.