How should the Rasha abandon his way?
Radak: In deed and verbally.
Why does it add "v'Ish Aven Machshevosav"?
Radak: Visible Teshuvah does not help unless it is also in hidden matters. A man's good or evil depends on the hand, mouth and heart; Teshuvah must be with all three.
Malbim: Teshuvah will help not only a Rasha who sinned due to desire. It is even for a sinner due to heresy and denial. He should abandon his false thoughts and begin to believe in Hashem.
Why does it say "[v'El] Elokeinu Ki Yarbeh Lislo'ach"?
Radak: This is even if a person increased doing evil.
Malbim: Some repent amidst love, for they recognize that He created the world - "v'Yashov El Hashem vi'Yrachamehu." Some repent amidst fear of punishment - "v'El Elokeinu", who supervise to reward and punish those who serve and rebel. Even though this is a low level, "Yarbeh Lislo'ach" (He pardons greatly).