Most directly? Well lets see... The first time the Russians, and the second time the Prussians. And no Wellington did nothing at Waterloo exept wait for an army of 170 000 Prussians that defeated the French army. He did not win the battle he survived it.
The Russian winter.
Massed British musket fire at the battle of Waterloo.
Napoleon Noticed Great Britain getting stronger and he attacked. He continued to attack any one that went against his rule.
In his memoirs Napoleon laid the blame squarely on the Peninsular War when he said that "All my disasters are bound up in that fatal knot".His attempts to enforce the Continental SystemHis refusal to restrict France's bordersHis decision to invade Russia
Yes very knowing he conquered most of europe before his downfall he had gotten so many enemies he could never hold them all off
his refusal to resrict fraces borders
Napoleon's horse at Waterloo was named Marengo, after the Battle of Marengo. It was the same horse that carried the Emperor at Austerliz, Jena and Wagram.
The 6 military coalitions formed against him whilst he controlled France. These always involved Britain, usually in alliance with any of the following countries: Austria, Russia, Prussia, Sweden, Naples, Portugal and various German States. For example, the 6th coalition included Britain, Austria, Prussia, Russia, Sweden and some German States. In Spain Napoleon suffered guerrilla warfare from Spanish nationals, holding down troops which could have been used in his 1812 Russian campaign. The event most immediate to Napoleon's downfall was of course his defeat at Waterloo to the British and Prussian armies in June 1815.
In his memoirs Napoleon laid the blame squarely on the Peninsular War when he said that "All my disasters are bound up in that fatal knot".His attempts to enforce the Continental SystemHis refusal to restrict France's bordersHis decision to invade Russia
You can tell throughout the last few years of Napoleonic rule the his judgement was declining; he had no real Navy, the Moscow campaign was a big failure; and he didn't think much of Wellington, which was a huge misjudgement on Napoleons part.
Napoleon lost in Spain and took a huge defeat in Russia. These two losses were two huge factors in Napoleon's downfall. His final loss was at the Battle of Waterloo in Belgium.