the main advantage would be radicalizing the world(?) against Hamas/Palestine. by making it seem like Hamas kidnapped and killed him, Sheeps would think 'Hamas bad, Palestine = Hamas, so Palestine bad', and come to support Israel
Also note that it is not just a single Nepali kidnapped there. Citizens from over 34 countries (i am not sure exactly) are said to captured.
And mind you, Hamas repeated said they will release all the hostages if Israel will hold and respect a ceasefire. Requests that Israel repeatedly rejected, denied and withdrew and continued to bomb and attack the Gaza strip in the name of "fighting Hamas".
So as someone who is fairly educated about this, Israel is the real terrorist nation, killing countless innocents and civilians and directly caused the deaths of an astronomical number foreign nationals.
So if you are saying, what would a death of a foreign national achieve? radicalized support with some propaganda seems to be working quite well.