In William Shakespeare's Julius Caesar, Caesar doesn't say the word "ambitious" in any form, makes no reference to being ambitious, says nothing that in itself would lead anyone to believe that he's ambitious, and does nothing to demonstrate that he's ambitious.
There's no doubt that Caesar was an ambitious man—his entire life is a testament to his ambitions—but Julius Caesar isn't about Caesar or Caesar's ambitions. The play is about other character's perceptions of and reactions to Caesar and his ambitions and about the aftermath of Caesar's assassination which was based on those perceptions.
Cassius is jealous of Caesar's and envious of his accomplishments:
CASSIUS. And this man
Is now become a god, and Cassius is
A wretched creature, and must bend his body
If Caesar carelessly but nod on him...
Why, man, he doth bestride the narrow world
Like a Colossus, and we petty men
Walk under his huge legs and peep about
To find ourselves dishonorable graves. (1.2.121–124, 141–144)
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