You Senpai is a person who is older/in a higher class than you. Since a senpai can differ from person to person this is everyone's senpai and out senpais your senpai by senpai.
Powers and Stats
Tier: The senpai of tiers thus they have no tier
Name: UNKNOWN (Due to one's senpai differing from another's)
Origin: Some weeb conversation
Gender: Ask Tumblr
Powers and Abilities: Being the best at literally everything. Better at everything that they are up against. Getting someone wetter just from making eye contact.
Attack Potency: Stronger than whoever they are facing against.
Speed: Faster than whoever they are facing against.
Lifting Strength: Look at AP
Striking Strength: Look at Lifting Strength
Durability: Nobody dares to lay a finger on Senpai
Range: Being graced with their presence is too much to bare.
Standard Equipment: Nothing really
Intelligence: Smarter than anything and nothing will be
Weaknesses: They are too perfect to have a weakness
Notable Attacks/Techniques: Noticing you. If you are noticed by senpai you collapse from the sheer amazingness and shock you receive. Nothing can and ever will be able to withstand this move and the opponent will always forfeit because of it.