buyers abusing returns process

I have been selling on Amazon since December 2016. I sell very expensive items and I know returns are part of the process but its got the point where I am becoming a lot less tolerant towards items that buyers send back because they say there is a defect and I get it back and theres absolutely nothing wring with it at all. Can I claim anything for that.

I had one guy and he bought a console from me, he then set it all up but then he said that he didnt play on it or test it or use it and then wanted a full refund because they said that they hadnt played on it.

I have another customer now who has sent back a console a couple of days ago because the item is no longer needed and I asked them if they had played on it or opened it up and they said they opened it to check it. They had the console for practically a month. I check the item and I can see that both controllers have been opened up and so has the console but they havent used the hdmi cable or usb cable. Should I give them a full refund, I wouldnt want to as it isnt right. I think they know that they are in the wrong because they are already saying that the will do chargeback with the bank. Its just if amazon would be more equal with buyers and sellers I would be a lot more inclined to give them a partial refund but the item is worth no where near as much used u see compared to new.

A lot of customers who buy fba are more likely to buy on a whim but they are more likely to return items compared to merchant fulfulled. It just annoys me how many times customers will say theres some thing wrong with the item and then i get it back and not only there isnt anything wrong with it all they have just returned because they have had there use out of it.