You must take revenge on Alfred for calling Alliana by annoying him 3 times.
this is earned midway through the Chapter. After the sequence of Jack and Alianna by the river you there will be a commotion and you find out the Earl has stopped the Monks using the Quarry.
At this point you will be back in control of Jack.
First Visit the Mill, It is located out of the Cathedral grounds, look for a water wheel on a building its on the right side of the map. Go inside and jonathan will be playing with Ants on the floor, pick up some Ants (remember to use your slingshot on the hornets nest outside the mill for another achievement)
Head Back to the Cathedral into the Cloister, you want to be in the area where the two youngs monks were talking at the beginning of the game and asked you what Gods temple was. You will find Alfred standing where they were.
1, First you will see Jonathan playing on the ground, equip the the quest icon revenge on Alfred and press
on jonathan, he will draw an insult on the ground.
2, Equip the SLingshot and Press Y to hit Alfred.
3, Equip the Ant and Press Y to throw them at Alfred.
After this Alfred will apologise and the achievement will unlock, it took about 30 seconds to pop so dont worry if it doesnt right away.