Wynut/Wobbuffett

Slow or fast? I can’t decide,
But training will fill me with pride.
It doesn't matter how slow or how fast it is because it will always attack last. You gain a lot of pride knowing that you can beat your opponent despite having to take hits first.

Physical strength, defensive skill,
Make fighting weaklings easier still.
They are defensive pokemon since they don't have any offensive attacks and they win by turning their opponents physical strength against them. This makes fighting weaker pokemon easier than stronger pokemon since the stronger pokemon might get a ohko.

I’d be a champ, I’d be a king,
But I’m stuck on a single thing.
They are stuck being defensive pokemon so they can't become champs since they are just as likely to lose as they are to win.

I need an aid to see it through,
But with help, I will shatter you!
The trainer provides the aid by trying to predict what the next attack will be so that they can properly defend against it. With that help they can win a battle.