There are different one-sided wars that have occurred in history. The Battle of Kiev is one of the prime examples. This battle happened in the year 1941. There were a million Soviet soldiers, but they lost the battle against the Germans in just three months.
The Battle of Omdurman is also another battle wherein the British were greatly outnumbered by the Egyptians and the Sudanese, but they were still able to win probably because of the various tools that they had. The battle of Carrhae is still considered to be one of the greatest fails of the Roman Empire. Crassus led 40,000 soldiers to their defeat against the 9,000 soldiers of the Parthia Republic.