Not all beams are meant to explode, surely the Z Senshi can control the effect of their attacks.
" @StargunZX said:
How then do explain times when the beams don't explode, but rather annihilate the opponent?
" @hitsusatsu11 said:
It does not change the fact that they often explode on contact with targets.
" Ki beams are actually specifically described as "bullets" in the daizenshuu"
What I'm trying to point is that the explosion rather than the initial impact (when a projectile strikes its target) or the pressure exerted before the projectile's detonation is most certainly the main destructive force behind those ki beams.
Like when Goku kills Tambourine, below:
This is also corroborated by the fact that beings are able to fight back the attacks, as seen when Freeza singed his fingers blocking and pushing back the kamehameha. Also with the Genki dama, and may other attacks, the opponent is simply vaporized with the attack itself.
Let's avoid no limits fallacy. ki beams will only collapse and detonate on contact with targets which are hard / durable enough to block them effectively. It's very likely that Vegeta's attack would have pierced a mile (likely much more) into the planet's crust before finally explode. And Freeza only touched the beam for a very brief moment, and he didn't kick it hard enough to make it detonate, but just to deflect it.
Furthermore, Vegeta's target was freeza, so according to you the ki ball should have exploded on contact. It didn't freeza overpowered it. "