General:
* Shout
* Scream
* Holler
* Cry out
* Roar
More intense:
* Bellow
* Howl
* shriek
More specific:
* Call out: To speak loudly to someone.
* Call: To shout to someone to get their attention.
* Demand: To shout something forcefully.
* Scold: To yell at someone for doing something wrong.
* Warn: To yell to someone to alert them of danger.
The best synonym to use will depend on the specific situation and the tone you want to convey.