Here is the full list of all 21 Time Carnage achievements.
Achieve Bronze in all challenges.
Complete the story on "Easy" difficulty.
Complete 4th Millennium on story
Complete Mesozoic Era on story
Complete 6th Millennium on story
Complete 4th Century BC on story
Played all modes
Achieve Silver in all challenges.
Complete the story on "Normal" difficulty.
Take no damage for an entire level in the story mode.
Shoot 250000 bullets.
Get 500 Headshots.
Survive 25 waves in Arcade
Kill 1000 Zombies.
Kill 1000 Skeleton Army.
Kill 1000 Robots.
Kill 1000 Dinosaurs.
Achieve Gold in all challenges.
Complete the story on "Hard" difficulty.
Unlock all the weapons.
Unlock all the perks.