Krishna is regarded by many Hindus as one of the most important deities in Hinduism. He is worshiped as the eighth avatar of the God Vishnu and also as the supreme God in his own right. He is the God of compassion, tenderness, love and is one of the most popular and widely revered among Indian divinities.
Shri Krishna is NOT the avatar of supreme God. Rather, "He" is the avatar of one out of the very few major God's (Energies) ranked below the supreme God.
Was He a real historic character or are the accounts of His life in Hindu sacred scriptures wholly mythical?
Yes "Shri Krishna" existed in the real history.
Another interesting thing I would like to add here is that.. Both "Parashurama" and "Krishna" were said to be the avatar's of lord "Vishnu", and they both existed in real history at one same time during Mahabharata.
Now, the more interesting question here is.. How come both "Parashurama" and "Krishna", two avatars of lord Vishnu, possible at the one same time ?
There's need to understand the term "Vishnu' to understand this puzzle.
"Vishnu" is NOT a living person, Its the "Rank" given to a certain "Energy" in Hinduism.
The only difference between "Parashurama" and "Krishna" is that.. "Krishna" was having this "Energy" / "Rank" by birth (Similarly like any child is born with a certain skill)
Whereas, "Parashurama" attained this "Energy" / "Rank" by doing Sadhana (Practice)
But, both were equal in powers.
Is there reasonable evidence to conclude Krishna was a real person or merely wishful thinking on the part of some Hindu scholars?
Only a face to face meeting with a person who has attained such powers can be the evidence. Rest everything is unsatisfactory.