YOU SAID:

I vow to not lose to anyone in my class

INTO JAPANESE

私は私のクラスの誰にも負けないことを誓います

BACK INTO ENGLISH

I swear that no one in my class will lose

INTO JAPANESE

私のクラスの誰も失うことはないと誓う

BACK INTO ENGLISH

I swear that no one in my class will lose