Which Sly Cooper Game is the Hardest to 100%?

Today we're talking about one of Sony's lost gems...the illusive Sly Cooper franchise...but we're not just talking about it. We'll be dissecting each game to understand which of them is the hardest to 100%.
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All the music used in this video is for entertainment purposes only. All rights go the copyright owners.
Music Used:
Sly 1: A Stealthy Approach
Sly 1: A Strange Reunion
Sly 1: High Class Heist
Sly 1: Mugshot's Turf
Sly 1: The Swamp's Dark Center
Sly 2: Museum
Sly 2: Paris
Sly 2: India
Sly 2: The Jungle
Sly 2 Contessa's Castle
Sly 2: Canada
Sly 2: Clock-La Battle
Sly 3: Blood Bath Bay
Sly 3: Opera House Basement
Sly 3: Hazard Room
Sly 3: General Tsao's Fortress
Sly 3: Battle with the Black Baron
Sly 4: Thieves in Time
Sly 4: Paris Rooftop
Sly 4: I smell a Rat
Sly 4: Clan of the Cave Raccoon
Sly 4: Here Comes the Grizz
Sly 4: Go West Young Raccoon
Sly 4: Sly Samurai
Sly 4: Merry Olde England
Sly 4: Forty Thieves
Starfox Assault: Briefing 1
Opoona: Mind Control
Food Delivery Channel: Ordering Party Food
Perona 5: The Days when my mother was there