No one can know the future if you are not Nostradamus  . I don't know which coin will be the most profitable, but if you believe what bullish trend promises this year, then all crypto. Grossly underappreciated coins can bring maximum profit. BTC already has a high price, therefore, it is hardly possible to make the most of it. I also doubt about ETH as it has already reached the previous high or so. I guess this is random and depends more on luck.  Almost no real control over this. Ordinary users can only manage the choice of the place of purchase and sale. To do this, you need to know what exchanges and what conditions they offer. The easiest way to find out is to use, for example, https://cryptototem.com/coinbase-review/ or similar.