The problem with stopping wars or similar is that, despite the maths on the ground (people killed by bombs today = 50 fewer than if Superman hadn’t turned up) such actions are rarely undeniably or purely positive. If Clark stops a Russian advance in Ukraine, well, that’s great for Ukraine and most surrounding countries and he’d be hailed as a hero by many people in Europe and elsewhere, but some - such as many Russians and those who fear that Clark is a particularly American power - will express disapproval and fear.
If Clark stops an Israeli attack on a hospital in Gaza or an Indian attack on a village in Kashmir, that gets even worse. Freeing prisoners from an Uyghur internment camp in Xinjiang? Freeing US prisoners from El Salvador? Kryptonite bullet time.