I made this topic for everyone that has ideas for new achievements. READ ON FIRST THOUGH!
First of all, I thought achievements could be divided into easy, medium, hard and extreme (or impossible or legendary, whatever sounds super hard). That way, new players can easily find out what achievements they could easily do and veteran players get to know what achievements give them a thrill to do.
Next, what many players probably want, new achievements. Different than the ones we have now. However, I fear somemay not be added though unless nide rewrites how achievements work. They are also harder and some may require rare items.
1. Headshot! - Finish a boss with a bow and arrow.
2. Burn, baby burn - Knock a player in lava and watch them burn to death.
3. Fus ro dah! - Knock a mob 10 blocks away, off a hill.
I ran out of ideas for now

~ Rob.