Eg: We have shirk and kufr, which is evil. -the goodness in that is that it clarifies eemaan. Because you cant see the difference between black and white until you see them both.

Death- makes us think about the Hereafter, encourages us to do good deeds.

Sickness is evil but if we remain patient it is something good because our sins are being wiped.

Abu Huraira related that the prophet (sallallahu alaihi wa sallam) said, 'for any trouble, illness, worry, grief hurt, or sorrow which afflicts a Muslim, even the prick of a thorn, Allah removes in its stead some of his (minor) sins"(Bukhari, Muslim)

When one of our beloved persons die, some people complain as to why he has died or they think its something evil. Whereas the prophet (sallallahu alaihi wa sallam) said 'Allah the Glorious says, 'I have no reward better other than Paradise for a believing servant of mine who is patient and resigned, when I take away one of his beloved ones among the most cherished things of the world." (Bukhari) so if this person remains patient then its something good but if he is not patient then it becomes evil.

Likewise Iblees is something evil but it is only evil if we follow him. If we disobey him and do not listen to him and refrain ourselves from the evil then it becomes something good because this is our way to paradise and we are rewarded by doing the good. So everything that Allah has created, has good in it and the evil comes if we use it as evil, so the evil comes from the creation as Allah says

"I seek refuge in the Lord of the daybreak from the evil of what he has created "(113:1-2)

So the evil comes from the creation.

"Evil has appeared on land and sea because of what the hands of men have earned (by oppression evil deeds) that Allah may make them taste a part of that which they have done in order that they may return." (30:41)

Evil is not an action of Allah otherwise a name would have been derived from it for Allah but there is not such a name. The goodness is attributed to Allah but the evil is not attributed to him because the evil comes from the creation depending upon how they use what Allah has created.

2. It manifests the names and actions of Allah such as severe in punishment, swift in reckoning, master of the day of judgement.

Had everyone been like the angels, Allahs names would not be manifested. Allah is also just, fair, and does everything with wisdom so he would not punish without reason for Allah is far removed from any defects and joking.

Allah's Messenger (sallallahu alaihi wa sallam) said "Verily Allah created mercy. The day he created he made it into one hundred parts. He withheld ninety nine parts and sent one part to all his creation. If the unbeliever knew all of the mercy which is in the hands of Allah he would not lose hope of entering paradise. If the believer knew of all the punishment which is present with Allah he would not consider himself safe from the hellfire" and in another narration "the remaining ninety nine parts of mercy which are with Allah is what he will use to judge mankind on the Day of Judgement."

So think of all the mercy of Allah only one part is in the fraction from which a mother feels mercy to her child, so if a person goes to hell he must really deserve to go to hell. Likewise when we sin, if we did not turn in repentance to Allah how would his attributes of forgiveness be manifest.

Allah's Knowledge and Wisdom