Two different things: a refund, which you decide, and a dispute, which the guest raises with their bank.
Refunding
In your Stripe dashboard, open the payment and choose "Refund", in full or in part. The money reaches the guest's card in five to ten days. The Stripe fees from the original payment are not returned to you.
Always tell the guest in writing, with the amount and the delay: half of all disputes come from a refund the guest thinks was forgotten.
A dispute is different
The guest goes to their bank. Stripe takes back the amount plus a fixed fee and gives you a short window to answer with evidence.
What wins a dispute
Written exchanges, the signed rental contract, the cancellation conditions as displayed at the time of booking, the confirmation sent, and proof the stay took place. Your website keeps all of it.