Plutarch, The Life of Cato the Younger 29

Metellus himself was still unyielding and bold, but since he saw that his followers were completely terrified before Cato and thought him utterly invincible, he suddenly rushed off into the forum, assembled the people, and made a long and invidious speech against Cato; then, crying out that he was fleeing from Cato's tyranny and the conspiracy against Pompey, for which the city would speedily repent in that it was dishonoring so great a man, he set out at once for Asia, intending to lay these accusations before Pompey. 

Accordingly, Cato was in high repute for having relieved the tribunate of a great burden, and for having in a manner overthrown the power of Pompey in the person of Metellus. 

But he won still more esteem by not allowing the senate to carry out its purpose of degrading Metellus and deposing him from his office, which course Cato opposed, and brought the senate over to his views. 

For the multitude considered it a token of humanity and moderation not to trample on his enemy or insult him after prevailing completely over him, and prudent men thought it right and advantageous not to irritate Pompey. 

After this, Lucullus, having come back from his expedition,⁠ the consummation and glory of which Pompey was thought to have taken away from him, was in danger of losing his triumph, since Gaius Memmius raised a success­ful faction against him among the people and brought legal accusations against him, more to gratify Pompey than out of private enmity. 

But Cato, being related to Lucullus, who had his sister Servilia to wife, and thinking the attempt a shameful one, opposed Memmius, and thereby exposed himself to many slanderous accusations. 

Finally, however, though he was on the point of being ejected from his office on the ground that he exercised tyrannical power, he so far prevailed as to compel Memmius himself to desist from his accusations and shun the contest. 

Lucullus, accordingly, celebrated his triumph, and therefore clung still more closely to the friendship of Cato, finding in him a great bulwark of defense against the power of Pompey.