Co-stars don't always have the best chemistry, and some actually loathe working together. Sometimes the rift is created by a personality clash while other times, it's the familiarity that breeds contempt. There's a lot that goes on behind the scenes, which can create extra drama on screen. The good actors can fake chemistry, making viewers none the wiser.
Ryan Gosling and Rachel McAdams

Worked Together In: The Notebook
Ryan Gosling and Rachel McAdams are the main loved-up couple in The Notebook, an iconic romantic movie about true love. There was no love spared between this on-screen couple who were rumored to despise each other. There's a fine line between love and hate, which is why this couple eventually ended up dating.