You will need to kill the Act I Boss, The Butcher, at least once over your four playthroughs (on Normal and Inferno), to get these two achievements. Complete the following challenges while fighting him to get the Fresh Meat achievement.
Stunning Reversal - Kill the Butcher while he is stunned by his own charge attack on Nightmare difficulty or higher
Don't Stand in the Fire - Kill the Butcher without being burned by floor fires or being grabbed by Ancient Spear on Hell Difficulty or Higher
A Brief Butchering - Kill the Butcher in under 2 minutes on Inferno difficulty