Tampering with screws, missing labels, unreadable barcode, broken ports, signs of water etc.. can also be reasons for rejection
More pictures and details in the attachment
CPUs
Bent Pins
Although bent pins can usually be repaired, CPUs like this are rejected as it is an obvious sign of physical damage.
Modern CPUs have Land Grid arrays which means that the pins will be on the motherboard socket instead. CPU RMAs can also be rejected if there is any scratches on the bottom/gold part of the CPU.
Missing Cooler
If the CPU came with a stock cooler this must be returned when claiming an RMA.
Look for missing CPU socket cover, bent pins and presence of thermal paste in the socket.
ALWAYS USE YOUR BEST JUDGEMENT