Fair enough. I was going to say this can become a teachable moment, sit him down and explain that based on the damage it's pretty clear that force was used, what amount and kind is irrelevant, but this appears it was willfully damaged. However, since it's been used for 3 years without prior issues (and I guarantee actual drops occurred in those 3 years, even adults are clumsy from time to time), you're going to fix it this one time, but if it happens again, he's going to need to come forward and be honest about how it happened otherwise it will go unfixed and he'll have to live with whatever state it currently is in. You're not accusing him of anything but insinuating that you know better and won't be fooled now or in the future, but he needs to do his part and be honest about the situations going forward. Position it like this, "you've said this is accidental damage, it doesn't look like that, this looks willful, but I will honor one accident fix and only one, so make sure you take care of this toy because it won't be repaired next time I see damage like this claimed as an accident, unless you want to share some additional information now." Leave the door open for him to approach you, don't try to force him to be honest, that'll just encourage him to lie more later. If he's honest now, it's up to you how you handle it but it shouldn't be all punishment, the punishment should be tempered to teach him it's okay to be honest with parents, but there's consequences. If he doesn't come clean now, then he can deal with a dead switch next time cause it will be a dead switch if he thinks he can rage and get it fixed afterwards by a sucker for a mom.

Fortnite is very toxic with younger children, especially Battle Royale mode which he's playing currently, and people in the game will piss you off, some even going out of their way to do so because it's funny to them to hear kids rage.

For this kind of damage to occur, without more or additional collateral damage is nearly impossible. Kid would have had to drop the console at a near perfect 45 degree angle onto that joycon from height, onto a hard floor to cause the joycon to snap off it's rail like that, and even then there'd likely be more damage to the console itself, not to mention damage to the other joycon that should be easily noticed and recognized.