Basically Shyvana is...

farm up or feed all game until you somehow get your frozen mallet then you auto win the game. Can't be killed, can't itemise against because she deals significant physical and magic damage and also has lots of attack speed, can't kite because she has too much movement speed and ult is unstoppable. Like who the actual fuck decided to make her ultimate unstoppable? It doesn't even have a cooldown. But Rito likes to keep problematic champions overpowered.