Give the sim the hot-headed trait, use angry paintings and a selfie taken when angry and just make sure you don't have things around that give them "happy" moodlets to counteract it (like decor, clean laundry, etc.)
There's also a recipe for making sims angry which a sim can make at cooking level 4 if you get them angry and a drink at mixology level 2; preparing those ahead of time will allow you to stack onto angry moods to help counteract any positives.
If you have Spa Day, do something for a few hours with the sim ahead of time that gives them the ability to surge emotions, which lets you pick the emotion you want the sim to enter. Painting works well for this.
Have the sim pursue the acting skill/career, and they can get angry by choice at will.
Seeing as you are just trying to tell a story, one thing a lot of simmers also do is use UI Cheats extensions so they can right click to remove the mood buffs they don't want.