The best way to compare this right now is... Hmm? Let's look at a boss.
There is a rock boss in the game -- you never got to him from what you've said -- who probably weighed as much as a large hill (about 200 tons or so). That guy decides to roll up into a ball and "tackle" Samus Aran at various points. That hurts, but not as much as you might think.
The closest thing to a "tank shell" you could use is Samus Aran's own missiles. They tend to pack quite a bit more punch, however. In Fussion, you get to meet "yourself" pretty early. You get hit by "your own" missiles, and you just get thrown back a bit and take damage.
I might be able to think of something with comperable power to those tank shells, though... Hmm? The anime and manga are the only things that come to mind as a tank actually targest her and shoots. The hit and following explosion only succeed in annoying her. In game... Maybe a machine boss. They have some pretty hard hitting shells, but it's nothing really impressive...
