Here is the full list of all 12 Flashback trophies - there are 7 bronze, 4 silver and 1 gold.
Kill an enemy by finishing him
Complete the game in Easy Mode
Complete the game in Normal Mode
Complete the game in Hard Mode
Kill 200 enemies with explosives
Kill 500 enemies with the Heavy Shot
Kill 50 enemies by finishing them
Conrad has to reach level 30
Obtain 100% in World Exploration
Kill 50 enemies with a melee attack
Complete all VR challenges
Obtain the maximum level for every upgrade