Loser is almost always a person. For example, the person who doesn't win the game, match, contest, etc. is the loser. You can't use failure in this sense. A loser can also be slang for a person who is completely unsuccessful in his/her life. It's an insult to say someone is a loser in that sense. A failure can be a person who is not successful in his/her attempt in a general sense. "He was a failure in the business world." Failure can also be a thing as "a failure to communicate", "a failure of a machine part", or "brake failure". In that sense, it means something didn't work as it was supposed to.

Loser has the failure.

- 'Loss' can be used to talk about money that has been lost by a business or an organization. It is the opposite of 'profit': 'Poor management resulted in huge losses.' It can also be used to mean 'the death of a person' or 'the state of no longer having something': 'We sympathize about the loss of your mother.' 'I am sorry about the loss of your home.' A 'loser' is a person who loses a fight. 'Failure' can be used to talk about a person or thing that has failed, or that often fails. It is the opposite of 'success': 'Was the scheme a success? ~ No, it was not. It was a complete failure.' = It was not successful. 'Everything in my life has gone wrong. I feel like a complete failure.'