The most OP character would be Kaguya with chakras and all powers of her sons Hagoromo&Hamura and Kinshiki&Momoshiki + also being able to use all of the unique/user specific Mangekyou Sharingan and Rinnegan techniques... on top of that, all the knowledge, skill/talent and experience of Orochimaru and Madara combined.

Hashirama McMadara von Kaguya Hagoromosson

I rest my case y'all can go home now

The most OP character is Masashi Kishimoto, 'nuff said

Teuchi

Dam man, I concede

This wouldn't be the strongest character but I've been wondering about it. A character with sage mode and byakugan. Wouldn't they be able to stop an opponents chakra control and insert natural energy into an opponent causing them to turn into one of those frog statues.

I think the enemy would sooner die from blows than natural energy. But hard to say, I have no idea how much chakra a single jyuken strike can force into opponent's body.

@SJ 88 @Bambusek
But nevertheless, the invisibility and the range of the attacks would be OP as hell.

Kaguya,with all the techniques of everyone in the Otutsuki plus all Uchiha,Uzumaki,Hyuga,Akimichi,Nara,Yamanaka,Aburame,Inuzuka,Lee and Kurama clan techniques.

Minato mixed with third Raikage, the fastest ninja and the ninja with the most brute strength and endurance. Teleporting around and able to slaughter anyone with one finger. Or Minato and Hidan, teleport close to the them, take their blood, teleport away and start the ritual, no way to ruin it.