The definition of evil is not something that can be concisely printed in one or two sentences or verses in the Bible. The intent of your heart plays a big part. We are ingrained in our flesh by sin, which is why evil comes from our heart, desires and such. What God creates is not evil by design. But humans, and angels, have shown the proclivity to twist what God has made into evil, and therefore God can say that He created evil since He created the possibility to cause evil. His intent was not for evil, yet He knew evil could spring forth.
A knife is not evil. It is a tool that can be used for good or evil. Peanut butter is not evil. Yet if you feed it to a child who you know is allergic to it, that would be evil. If you feed peanut butter to a child who is allergic to it without knowing they are allergic, that is not evil, yet a bad result can happen. The same can be said for what we speak to others. We may have good intentions speaking in love for the person, yet it can be taken the wrong way and hurt can result. Some think they are speaking or acting from a place of love but in reality they are speaking or acting from their desire to fix the other person or show them how to live the right way. When we are honest with ourselves, we will find that we end up like Paul did in Romans 7:
5 For when we were in the flesh, the sinful passions which were aroused by the law were at work in our members to bear fruit to death.
6 But now we have been delivered from the law, having died to what we were held by, so that we should serve in the newness of the Spirit and not in the oldness of the letter.
7 What shall we say then? Is the law sin? Certainly not! On the contrary, I would not have known sin except through the law. For I would not have known covetousness unless the law had said, "You shall not covet."
8 But sin, taking opportunity by the commandment, produced in me all manner of evil desire. For apart from the law sin was dead.
9 I was alive once without the law, but when the commandment came, sin revived and I died.
10 And the commandment, which was to bring life, I found to bring death.
11 For sin, taking occasion by the commandment, deceived me, and by it killed me.
12 Therefore the law is holy, and the commandment holy and just and good.
13 Has then what is good become death to me? Certainly not! But sin, that it might appear sin, was producing death in me through what is good, so that sin through the commandment might become exceedingly sinful.
14 For we know that the law is spiritual, but I am carnal, sold under sin.
15 For what I am doing, I do not understand. For what I will to do, that I do not practice; but what I hate, that I do.
16 If, then, I do what I will not to do, I agree with the law that it is good.
17 But now, it is no longer I who do it, but sin that dwells in me.
18 For I know that in me (that is, in my flesh) nothing good dwells; for to will is present with me, but how to perform what is good I do not find.
19 For the good that I will to do, I do not do; but the evil I will not to do, that I practice.
20 Now if I do what I will not to do, it is no longer I who do it, but sin that dwells in me.
21 I find then a law, that evil is present with me, the one who wills to do good.
22 For I delight in the law of God according to the inward man.
23 But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members.
24 O wretched man that I am! Who will deliver me from this body of death?
25 I thank God--through Jesus Christ our Lord! So then, with the mind I myself serve the law of God, but with the flesh the law of sin.
We truly have to renew our minds daily, resetting our mindset to the Spirit of God since we are tied to our sinful flesh in this world. Paul saw that he strove to do good, yet evil often sprang from his intent. Romans 7 is incredibly difficult for me to wrap my head around but it does clearly spell out the conundrum we face as depraved humans, and why we need Jesus.