It's kind of hard to tell much from the photos because of the blurriness, but he definitely has some significant fin damage. If its fin rot, the edges of the fin will have blackened or possibly bloody tips.
It'll be a lot easier for us to help if you give some more information. I know hes not in your main tank right now, but still try to fill this out for him to the best of your ability.
What size is your tank?
What temperature is your tank?
Does your tank have a filter?
Does your tank have an air stone or other type of aeration?
Is your tank heated?
What tank mates does your betta fish live with?
What type of food do you feed your betta fish?
How often do you feed your betta fish?
How often do you perform a water change?
What percentage of the water do you change when you perform a water change?
What type of additives do you add to the water when you perform a water change?
Have you tested your water? If so, what are the following parameters?
Symptoms and Treatment
How has your betta fish's appearance changed?
How has your betta fish's behavior changed?
When did you start noticing the symptoms?
Have you started treating your fish? If so, how?
Does your fish have any history of being ill?
How old is your fish (approximately)?
Also, for future reference, topics like this one should be posted in the 'Betta Fish Diseases and Emergencies' section of the forum. You won't get in trouble for posting here this time, so no worries, but just know that for the future.