World 1 is the easiest for obvious reasons. This was the last achievement I got so I had a few upgrades: Range Up Lvl 4, Fire Rate Lvl 4, as well as the Shield and Power Up abilities to aid me in getting this achievement.
I would advise taking it slow, killing as many enemies as you can, there's lots of given time to do so, and keep an eye out for spikes, floor panels, and hidden books. Take time to scan to area around you to be safe and you should be able to complete World 1 without losing a life quite easily!