From The TimeSplitters Wiki

Stain Removal
IMAGE NEEDED
Game	TS2
Section	Glass Smash
Map	Notre Dame - Cathedral Upper Floor
Character	Undead Priest
Enemies Encountered	N/A
Rewards	Silver: Hunchback
Medal Requirements	Bronze: 23 points Silver: 28 points Gold: 32 points Platinum: 32 points and 47.0 sec.

Stain Removal is mission done in Notre Dame. You need to shoot beautiful glass art into shards, using Grenade Launcher.

Briefing

In this challenge you got to take out all the stain glass windows in the

church. Only use the secondary fire, as the flaming grenades go further than
the normal ones do (and look somewhat nicer).

Strategy

Take out the three on your left, then strife right and fire at the ones above

opposite you. When you reach the end, take out the square window at the top,
the four next to it, then the three below them. Now go left of the column
ahead of you and take out the far window that was to the left of the three
you just shot at. Turn around and go as far left as you can so you can get the 
one that was behind you. Go back to where you started and strife left down
the other side, while taking out the ones opposite as you go. When you stop,
shoot the square window at the top, the four to the left of it and then
the three below them.