Here is the full list of all 73 Second Chance Heroes achievements.
Kill a Blood Top
Kill 5 Vampires
Kill 10 Werewolves
Kill 20 Karate Klutz
Kill a Giant Karate Klutz
Kill A Sentient Cheeseburger
Kill 50 monsters
Kill 1,000 monsters
Kill 10,000 monsters
Kill 25,000 monsters
Kill 500 monsters
Kill 5,000 monsters
Play a level as each character
Play as each of the less reputable Heroes
Play as both Joan of Arc and Napoleon
Play both Caesar and Cleopatra
Play as each melee character
Play as every scientist
Play as every female character
Open 10 chests
Open 50 chests
Open 100 chests
Beat the first level
Complete every level in the game
Complete all Hobo Colony levels
Complete all Mall levels
Complete all Bunker levels
Kill every boss
Kill one of each specialty monster
Kill W.A.R.D.
Kill an Amazing Head
Kill 5 Fat Army Privates
Kill 25 Fat Army Privates
Kill Beelsteambub
Kill 10 Body Parts
Kill a Burglar
Kill 5 Charlies
Kill 25 Sentient Cheeseburgers
Kill 5 Commandos
Kill 25 Commandos
Kill Private Corpsepile
Kill a Crazy Cat Lady
Kill Dr. Neirzeit
Kill 25 Fast Food Fatties
Kill 5 Goats
Kill 5 Zombie Hobo Warriors
Kill 100 Zombie Hobo Warriors
Kill 25 Zombie Alien Hybrids
Kill Johnny Hollowlegs
Kill 150 Karate Klutz
Kill Mad Mulligan
Kill The Mallrog
Kill Mama Nibbles
Kill 50 Nibbles
Kill 25 Roach Knights
Kill 10 Robots
Kill 150 Robots
Kill 5 Super Heroes
Kill The General
Kill The Turtle
Kill 50 Vampires
Kill 250 Vampires
Kill The Walrus
Kill 100 Werewolves
Kill 500 Werewolves
Kill Zombilly
Collect 1,000 XP
Collect 10,000 XP
Collect 100,000 XP
Collect 200,000 XP
Collect 25,000 XP
Collect 5,000 XP
Collect 50,000 XP