It will absolutely be several altcoins that will increase this year but it will be a lot more that actually will decrease. In an uncertain market who demand plays a big role, there will always be projects who are going to fail. I have listed out three Altcoins that I believe will lose a lot of value in 2021 for various reasons. 

1. Basic Attention Token 

I would say that BAT has an excellent team behind them and it is a reliable cryptocurrency in general, they have their brave browser that in my opinion is one of the best search engines out there, but if we are going to talk about their token, I have a lot of cynical things to say. I know it harsh to say, and maybe an uptrend would change my mind, but no it doesn't, actually it pretty obvious that the cryptocurrency has decreased with the bearish run that has been through the market. 

2.
Cardano 

If you had proposed to me a year ago about Cardano, I would be very optimistic about the project but right now with a half-decent testnet and a growing point of hardly 3 percent this month then I see this as a nonvolatile coin with low potential. Cardano has had its golden days and I believe it's time for me to sell most of my holding and invest in something else. Do not take this as written in stones because you know how cryptocurrency is and maybe Cardano will have an upswing in the coming months and from that perspective it could be a great idea to invest in this "under-valued" coin. 

3. XRP                                                                            

I has since 2019 been an active investor in this coin and right now my XRP portfolio is down by like -30% so this is clearly my biggest disappointment. I am not going to keep my holdings because I really want it to increase a little bit before I sell it and by just saying that you will see a lot of warning signs there.