Who's the strongest foe that the *other* Z-Fighters can beat?

[Cyke]

So, let's take the Saiyans out of the equation. This is the team at their current and/or prime levels (whichever one is highest), including the current Super manga. The line-up is as follows:

Piccolo
Android 17
Android 18
Yamcha
Tien
Chaozu
Krillin
Roshi
Good Buu (optional)

Round 1: Who is the most powerful single foe that they can beat? Who's the weakest that beats them?

Round 2: What is the most powerful established team (any genre) that they can beat? Likewise, the weakest team that beats them?

Standard Khazan arena rules apply.