Is it cheating if you use a very strong pokemon card?

my brother is accusing me of cheating when i had a mew, lucario, lugia, mespirt and luigi(fake). Luigi has 99999 HP and has an attack with 100 damage. he is accusing me of 'cheating'. when i use my supreme blast with mespirt,(200), this is ALSO 'cheating'. HES A DOUCHE BAG! IS it cheating?