Stubborn
noun, な adjective
A hard stubborn person is very stubborn no matter how you look at them. Try to break through that hard stubbornness and all you'll find is more stubborn.
がんこ
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
アイツ、めっちゃ頑固だよ。
He is really stubborn.
これを使うと、頑固なシミもすぐ落ちるんだって。
I heard that this can remove stubborn stains quickly.
おじいちゃんって頑固者だよね。
Grandpa is stubborn, huh?