Step up Quests

Im having trouble with the 4star step up Diablos. I hit him with a special and he eats it like an apple while maintaining eye contact. Then he lowers his horns like a freaking battering ram and one shots me. If i turn the audio up to max i swear i can hear it laughing. Please advise

・Upgrade your weapons and armor
・Carefully observe the monster’s movements and attack during openings
・If you think a high-damage attack is coming, use your SP invulnerability to negate it while counterattacking

Fortunately, you can challenge Urgent Quest monsters as many times as you like, so keep trying
Even just observing their behavior patterns is worthwhile
It might be a good idea to start by practicing how to move without taking damage

It’s hard to give advice without knowing what armor you’re using.
Personally,
I think a Guard Reload Gunlance stacked with Guard might be good.