Depends on what He is dealing with. Evil with "evil" and good with good. Clearly stated..abhyudhhanam adharmasya, parithranaaya sadhoonam... sambhavami yugay, yugay.
Godhead is Nirguna, there is neither good or evil. Let me explain what I mean by "evil" ( in quotes) of Divine initiative. It is just His Leela.
True devotion with Dharma has given peace and happiness to the man and God, good is well known and harmony is experienced.
However in the re-establishment of Dharmic order Lord Rama and Krishna respectively had to resort to what may at the time appear out of proper limits. To appreciate this (who are we to do that?) one has to ponder over the magnanimity of the task for which Avatars had to be assumed by the Supreme for annulment of evil.
In case of Vali a boon to acquire power of his opponent during battle is quite unfair and formidable, needing to deliver a killing arrow at Vali's back by Rama.
In case of Duryodhana (tacitly and dishonestly supported by father Dritharashtra) Kauravas' diabolic unfairness to share in the kingdom even smallest extent (unwilling to allot even five small towns to those who were otherwise equal royal inheritors of Hasthinapur kingdom) it became imperative (among many other strategies and initiatives by Krishna) to spread an untruth [Ashwathhama hathah( but only a kunjaraha !)] in order to demotivate an adversary's army commander Drona for further continuous participation in fierce battle Kurukshetra ...or earlier Krishna's pretending to have not even seen Duryodhana's arrival when he came to seek His support.. because in the alternative scenario when supporting un-sharing possesive evil of the Kauravas the main purpose of Krishna Avatar would have been wastefully compromised..
The Supreme spirit is ever loving. But has a purpose and self-given Dharma protection responsibility in each Avatar. In Ramavathar, Soorpanakha when out to seduce Rama, he had to arrange to have her nose cut off; in Krishnavathar even after opportunity of 100 misdemeanors was granted, a violation spree by Dusshasan led to his decapitation.
It is not evil, it is countering evil in these and many more cases.
Seen in a wider context.. Self-defence in perilous times that comes instictually .. such a so-called "evil" is an integral part of Swadharma.