Question

Which nation leader would be forced to call a new election after losing a vote on a major issue in legislature?

Answer 1

In a parliamentary system, representatives are elected by the people. That forms the legislature or parliament. The parliament then choses a prime minister and other executive officers.
If one party has a majority of votes in parliament, the leader of that party becomes prime minister and other executive offices are filled by other members of the party.
When one party doesn't have a majority, leaders of the various parties work out a coalition to get enough votes for a prime minister. So the different executive offices would be filled by two or three different political parties working together.

If the prime minister puts forward a bill that is not supported by a majority of parliament, it shows a lack of confidence in the executive part of government. If the issue is big or if he keeps losing then new elections have to be held. A new set of representatives are chosen and the process of forming a government starts again.