The best way to end an unnecessary debate is to agree with the opponent. The opponent is happy that you have accepted your defeat, you are happy that you can go on with your work and life. The only thing you would need to keep in mind is to avoid the opponent next time. Save your energy for more constructive things in life!

In Bengali - "Pora shuna shikhey jantu hoyar thekey, aggo hoye bhalo manush hoya bhalo"
Translation - "Instead of being an educated animal, it is better to be an illiterate human"
~ My dad