Is it me or just it seem totally unfair champions can build mostly tank item and be just messed up

so just played a game an udyr build the ap jg item an trinity force an was just broken, he had like 130 mr and armor mid game an it felt like we weren't even touching him but he could legit tower dive us an kill us(even in base) an just speed away. What do u do in such stressful situations, split pushing doesn't exactly work an what do u do when champions build mainly tank an do ridiculous dmg.