There are three times recorded in the Bible where Satan spoke, on each occassion slander is at the root of it.

Genesis 3

Here Satan maligns God's character and reputation.

The answer to that is found in Revelation 12:11 on the lips of the redeemed who "triumped over him ... by the word of their testimony".

I don't have the testimony that when I was prayed for while unconscious in a hospital bed I leapt up and caught the train home with my wife - which is what I longed for, but I do have the testimony that God is Good.

I don't have the testimony that when my wife was terminally ill I got her back - which is what I longed for, but I do have the testimony that God is Good.

I struggle with not knowing the plan, but I trust the planner. Ephesians 1 "... He has blessed us ... He chose us ... He has freely given us ... we have redemption ... we are included in Christ ... we have received the Holy Spirit".

There are some good things I should avoid, or God, in his goodness, keeps away from me. Not because they are not good, but because I could not handle them. A good gift in the wrong hands or at the wrong time could be destructive. Proverbs 20:21 "An inheritance gained hastily will not be blessed in the end".

Need to test whether "the good is God", the goodness of God is unquestionable.

Job

Here Satan maligns both God's character and reputation, and Job's motives.

In both prosperity and disaster Job did not dishonour the name of his God. Proverbs 30:9

Job 13:15a "Though He slay me, yet I will hope in him".

Matthew 4:1-11

Here Satan questions Jesus' Sonship and position declared in Matthew 3:17 "This is my Son, whom I love; with him I am well pleased".

v3 Not performed a miracle yet?
Here's one you can safely try while no one is around.
It'll just be between you and me that this miracle stuff does not work.

v6 Afraid of the depression which will set in if first miracle does not work?
Don't worry, if this one does not work out you won't be around to get depressed.

v9 Still want wealth, power, reputation?
Easy, just come and work for me.

What about your standing in Christ?
Maybe Satan does not need to speak to you - you do his job for him...

There is the old song "What a wonderful Saviour is Jesus".
There will never be a song "What a wonderful Christian is Jonathan".

BUT!
Isaiah 61:10 I will rejoice greatly in the LORD, My soul will exult in my God; For He has clothed me with garments of salvation, He has wrapped me with a robe of righteousness.
John 1:12 To all who did receive him, to those who believed in his name, he gave the right to become children of God.