Be sincere will you return back to the address that mistakingly sent you 100BTC?
If he can provide proof that he owns that address to me,then i will consider returning the amount ofcourse less fees,because I dont want that bitcoin stays on another hand or i will be sure that he is not a hacker that's why he mistakenly sent that on my wallet
Another thing is,i will decide when that situation happens lol.because 100btc is not a small amount that can change life if the recipient is greed and not good person