Sometimes, when we’re describing something that happened, we want to bring attention to who is doing the action. In this case, you can use c’est...qui.
C’est Marie qui joue au tennis.
Marie is the one who plays tennis.
C’est moi qui ai attrapé le ballon.
I’m the one who caught the ball.
Even if there are several people doing the activity, you will still use est.
C’est nous qui chantons.
We are the ones who are singing.
If you got hurt, you can use se faire mal in passé composé. You can get more specific, though, and tell someone where it was you got hurt. To say this, you use au (or à la, à l’, or aux, depending on the gender) after se faire mal.
Nous nous sommes fait mal en tombant.
We got hurt while falling.
Elle s’est fait mal à la jambe.
She hurt her leg.
Tu t’es fait mal au pied.
You hurt your foot.
As you can see, we use the same form fait mal for all the sentences.
If you do an activity in the best way possible, you do it le mieux. As you can see from the following examples, le mieux doesn’t change.
Cette équipe joue le mieux.
This team plays the best.
Ce joueur de handball saute le mieux.
This handball player jumps the best.
When something is the worst, it’s le pire (or la pire or les pires, depending on gender and number).
Cette situation est la pire.
This situation is the worst.
Ce sont les pires athlètes.
They are the worst athletes.