which country does it belong to ?
In those nations which still, in theory, permit the Monarch to withhold assent to laws such as the United Kingdom, Norway, and Liechtenstein.
Royal assent
in those nations which still, in theory, permit the Monarch to withhold assent to laws (such as the United Kingdom, Norway, and Liechtenstein), the Monarch almost never does so, except in a dire political emergency or upon the advice of their government. While the power to veto a law by withholding royal assent was once exercised often by European monarchs, such an occurrence has been very rare since the eighteenth century.

when was the last time an english monarch vetoed an act of parliament UNANSWERABLE what is this topic about? Royal assent is the method by which a monarch formally approves an act of the legislature.
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Royal assent [SEP] Introduction
While the power to veto a law by withholding royal assent was once exercised often by European monarchs, such an occurrence has been very rare since the eighteenth century. Royal assent is sometimes associated with elaborate ceremonies. In the United Kingdom, for instance, the Sovereign may appear personally in the House of Lords or may appoint Lords Commissioners, who announce that royal assent has been granted at a ceremony held at the Palace of Westminster for this purpose. However, royal assent is usually granted less ceremonially by letters patent. In other nations, such as Australia, the governor-general (as the Monarch's representative) merely signs a bill.