Zamoyski in the introduction to his biography of Napoleon has some interesting insights:
"In the half-century before Napoleon came to power, a titanic struggle for dominion saw the British acquire Canada, large swathes of India, and a string of colonies and aspire to lay down the law at sea; Austria grab provinces in Italy and Poland; Prussia increase in size by two-thirds; and Russia push her frontier 600 kilometres into Europe and occupy large areas of Central Asia, Siberia, and Alaska, laying claims as far afield as California. Yet George III, Maria Theresa, Frederick William II, and Catherine II are not generally accused of being megalomaniac monsters and compulsive warmongers.
Napoleon is frequently condemned for his invasion of Egypt, while the British occupation which followed (...) is not."
For Charles Esdaile the Napoleonic Wars started in 1803, and Napoleon bore the entire responsibility:
"Let us begin by discussing what we mean when we say the Napoleonic Wars. Hostilities broke out on 18 May 1803 when Britain, pushed beyond endurance by repeated acts of aggression and hostility, declared war on France and her new ruler, the so-called First Consul, Napoleon Bonaparte." (from the introduction of his Napoleon's Wars)
If Napoleon can be considered a warmonger because he responded to aggression by Great Britain in 1803, Austria and Russia in 1805, Prussia and Russia in 1806 and 1807 and Austria again in 1809, then I would think that a new definition of 'warmonger' should be considered.