Frisk is the protagonist of the game. They are officially described as someone kind and understanding. But it's only up to the player to decide whether they are merciful or murderous. I don't have any voice preferences since its age and gender are very variable depending on which AU. The lines that I give for this role are really just examples (understand by that : not an obligation to do them). If you want to do other lines that imply a specific gender more than another, you're welcome to try. So, show me your interpretation and the best you can do with it ! :)