He was only 'grenade-level' after being severely weakened. As has been stated time and time again on these threads, DBZ characters weaken in all aspect as they lose ki.
As for the Roshi thing, the RR Army had quite a few resources; including hitmen such as Pai Pai, amongst other things.
Tao was quite confident that the grenade would hurt Goku, who was at full power.
And he used that as a final resort, meaning he considered it to be much stronger than his normal attacks (or strong enough to hurt someone of his own level).
Your argument of 'he's small, so only a bit of the blast will affect him' is pretty silly. If a person gets hit by a nuke with an blast radius of 5km, and another gets hit by one with a radius of 10km, both will be destroyed just as well.
The person is still tanking only a fraction of the blast. He gets destroyed because the person is weak, while Toriko isn't.
Divide the area of Toriko's body to the AoE of the explosion. That's the fraction of the country buster that Toriko tanks.
Where the heck are you getting the 'Toriko is faster' thing from as well? The last time I checked, Toriko wasn't DBZ level in that department.
Toriko verse has speed feats exceeding mach 600+. When does Nappa display 'this' level of speed? Goku, who thrashed Nappa takes 28 hours to cross 1000,000 km.
Doubt if Nappa's even in the triple digit range, let alone Mach 600
Which is why Goku was shitting himself, clearly. And Tao only threw it as a last resort because he had nothing left.
As for the AoE thing, well that's just dandy, so by your logic a cero from one of the espada would do just as much as a planet-buster? Thank you for your input.
Speed feats exceeding mach 600+, you say? Where was this stated? Or is this another calculation from your beloved OBD?
If you are going by calcs, allow me to re-post one of my own. I used this a while back, I think it might have been in a Star Wars vs DBZ thread.
'Without having to charge up, Piccolo fired off a beam that reached the moon in the space of a few seconds.
Now the usual response to this would be "but that was anime only, we don't know how long it took to reach the moon in the manga."
I don't mean to insult your intelligence with this or anything, but just to remind ourselves of the ground facts.
The speed of light is 299,792,458 m/s. The distance between the moon and the earth is generally held to be 384,400km (384,400,000m).
Now let's consider the scans to refresh our memory:
We notice that Piccolo is in the exact same position when he fires the blast and when the moon is gone. This strongly suggests that very little time has passed at all. What reinforces this case is that Gohan (as an Oozaru) was firing off energy blasts everywhere. It is therefore ludicrous, having noted these points, to say that the beam could have taken much time at all to reach the moon. Piccolo could not have remained stationary whilst in danger of getting hit by an oozaru blast, nor would he have just sat there in the exact same pose.
So, getting to the numbers, being harsh on DBZ, let's say no more than 10 seconds could have passed (IMO it would have been less, more like 5, but I'll be lenient).
384,400,000m/10s gives a speed of 38,440,000m/s. That means Piccolo's blast was moving at over an eighth the speed of light if we go by this, putting it firmly in relativistic territory. This was a Piccolo with a PL of less than 500.'
That was what I stated. From this, you could argue that Nappa has relativistic reaction speeds, given that he was well above Raditz who easily dealt with this Piccolo.
And for everyone saying that Nappa would not resort to the two fingers of doom, I'd ask you to rethink. It's become his signature move, an attack that he used casually.