Fight with Vali and lose 50%?

Vanara King Vali ruled Kishkinda. he was a great warrior even Lord Rama and Lord Hanuman had a great respect for his bravery.

Vali character in Epic Ramayana is portrayed equally to Karna(friend of King Duryothana of Epic Mahabharat). Both are good in nature and possessed immense power to destroy their enemies and
Finally, they got killed pathetically.

Here
There is a belief “If any Warrior fights with Vali. the Warrior loses half of his power to him”
So
Vali gains 50% of the power of his enemy. It’s a myth?
NO,
See Vali was a great warrior. How did he defeat King Ravana (a great villain in Ramayana)?

A great warrior studies the power of an opponent before going into war. He analyses the opponent’s entire skill, past victories and his plus and minus. Then he prepares accordingly to defeat him. Here this process made him to win over his enemy and Analyzing the opponent there he adds opponent skill to his… this was later told that he earns 50% of the power of his defeated enemies..