violation punishments

As smwutches mentioned, enforcement.xbox.com. Of course if it were up to me, and i headed the enforcement team, i would place a permanent ban on any one using a "modded controller." Im a firm believer in fair play and ppl that have to cheat doesnt need
to play. Call me extremely strict but thats just me. Gaming should be fun and fair for everyone

You also shouldn't discuss modifications on the forums. Console modifications breaks the ToU and is mentioned in the Code of Conduct as a no no. Modifications tend to lead to a total console ban but as Smutches states, that is all dependant on the Enforcement
team and they do not use the forums.

What are the punishments for different types of violations, for example using a modified controller.

Typically enforcement does not publish what actions are taken against a violation as many times it is also dependent upon the history of the individual / or gravity of the infraction.

Here is a link to the current Terms of use: https://www.xbox.com/en-US/legal/xboxComTOU

That would be up to the enforcement team. You can read about some types of enforcement actions at https://enforcement.xbox.com/en-US/home/howto#sub-topic0-2

There was a violation in some post from looking for groups, friend.

The responsible team analyzes the punishment, and if confirmed, sends the punishment.