As a customer he was supposed to go through everything too as all customer goes to everything before buying.
In an informal setting like FB, you should make your refund policy clear to the customer when you're conversing with them. The only reason why you didn't is because you thought you'd lose out on the sale. You're not an established and well-reputed retailer with a trusted payment processor, you're an individual with a cellphone, bank account and a facebook profile.
Once it left I can't help it can't cancel.
This is a lie. Shiprocket makes it easy to cancel and RTO (return to origin) a shipment at any time after pickup. The truth is that you didn't want to pay RTO charges (which are usually the same or less than the actual courier charges).
that kid was meddling with xmp on his own doing custom profile for oc on his ram
The kid here is you, and this is proof. You can't mess up a motherboard or ram by 'custom oc profiles for ram'. But you lack the technical experience to realize this, making you the kid.
Stop being annoying and put out fake story.
It's clear to see that the only fake thing here is you, pretending to be a reseller that can be trusted.
Once it's left we are done we are not Amazon that takes back parcel and do whatever they want.
And that's why you're struggling to retain customers. No amount of discount would replace peace of mind when making expensive purchases.
I believe you as his prices were higher than what others offered me lol.
I purchased from him back when he was active on the forums, most of this stuff was mining related (RMA'ed PSU's and used GPU's). For items that weren't sealed, he'd make a video showing that it was working before packing the item and sending it. There were even times when GPU's failed furmark so he refunded in full even though he had other GPU's I was interested in. But I haven't dealt with him in over a year, hopefully he hasn't changed.
In fact, this has become common practice with many of the OLX/FB sellers I interact with. They'll also do other tests if you ask them to (check all sata ports are working, turn on xmp, check all fan headers are working) and send videos as proof before accepting payment. But if the product is sealed, then the only way for a resolution is through RMA.
For new sellers, I insist on a photo of their ID, and I give them mine in exchange. This is enough of a hurdle that it'll weed out the disreputable sellers.