I bought one of the toolkits from CT and was not satisfied as the tools were not picking the thread properly. 15 days later i went to return but CT refuse to refund the money. They said that since its been used they cannot give a full refund. Can i sue them?
Anybody who wants to can sue anyone for anything. If you live in a province with strong Consumer Protection legislation, and the product has a clear manufacturer´s defect, then you have a good basis to sue. Contact your provincial Consumer´s Ministry for detailed advice.
The real questions are 1) are you likely to win a lawsuit, and 2) would it be worthwhile to try.
There is a cost to filing a lawsuit, so unless the toolkit was expensive, it´s probably not worth bothering. Do what you can within the stupid store policies. If that doesn´t work, you can threaten to sue, and maybe they will back down.
Despite the legislation, many items CT sells have a no-refund policy, even though they are not clearance items. This means that store may try to get out of giving you a refund, and instead only exchange it, or send it out to be repaired. You can get an idea of the policy by checking their web sites, but the only ways to know for sure is to call their 1-800 number, or check with Customer Service in the store. Even then, you may get different answers.
You may have to just take it as a life lesson that CT sucks and not to shop there for anything that might possibly be defective.
Finally, some customers have decided to return the item as just unwanted, without letting the store know that it was defective. Ironically, the stores are happier taking something back if they think they can resell it, because they might lose money if the item is defective. The store you bought it from might be harder to deal with, and another store nearby might be more lenient.
Or, you can listen to the lawguy person, blame yourself, and just give up. However, if you read lawguy´s posts, it´s obvious they know very little about the law, and even less about CT´s policies. However anyone who wants to can sign their post as being from lawguy, so you never know who you are hearing from.