Bodyguard Trophy in The Psychoduck

Story related. Cannot be missed.

Beginning with the second level, the heron's bodyguards will start to appear in each of the game's later levels. On top of that, grey blocks will also appear that will allow the duck to hide behind them so he can prevent the guards from sensing his presence.

Once the guards are away from your line of sight, you should safely try to duck and sneak up by the heron and kill him as you did previously in the first level before they walk up and find out that you are in the vicinity of the level, regardless if you are standing or crouching.

You will unlock this trophy once you complete the second level for the first time.