Here is the full list of all 19 Angry Video Game Nerd Adventures achievements.
Beat the game over Halloween weekend on Normal or Higher difficulty
Beat the game on "Old School" or higher
Found Matthew Lentz
Find all S*** Pickles
Find all the cameos
Beat the game on "Normal" or higher
Find Craig
Die 1000 times
Kill Naggi
Collect 200 1ups
Ride the Fire shark
Find all playable characters
Enter a cheat code
Drink 100 beers
Kill Santa
Die 100 times
Beat the game on "Hard as Balls" or higher
Beat the game on "Impossible" or higher
Beat the game on "YOLO"