All the options/actions available to the player in the Ivan The Not So Terrible mission.
The first mission where Niko faces a moral choice (execute/pardon).
If Ivan survived, then later he (Ivan) can be found as a random character in Alderney (access there opens after the Three Leaf Clover mission).
If the player (Nico) decides to execute Ivan, Ivan will not be encountered as a random passerby in Alderney (after completing the Three Leaf Clover mission). However, Vlad will give the reward ($200) to the protagonist anyway.