wicked

Proverbs 10:26 As vinegar to the teeth, and as smoke to the eyes, so is the sluggard to them that send him.

Proverbs 26:6 He that sends a message by the hand of a fool cuts off the feet, and drinks damage.

Jeremiah 23:13-16, 28 And I have seen folly in the prophets of Samaria; they prophesied in Baal, and caused my people Israel to err...

Ezekiel 3:18 When I say to the wicked, You shall surely die; and you give him not warning, nor speak to warn the wicked from his wicked way...

Ezekiel 33:7, 8 So you, O son of man, I have set you a watchman to the house of Israel; therefore you shall hear the word at my mouth...

2 Corinthians 2:17 For we are not as many, which corrupt the word of God: but as of sincerity, but as of God, in the sight of God speak we in Christ.

but

Proverbs 25:13, 23 As the cold of snow in the time of harvest, so is a faithful messenger to them that send him: for he refreshes the soul of his masters...

1 Corinthians 4:2 Moreover it is required in stewards, that a man be found faithful.

2 Corinthians 5:20 Now then we are ambassadors for Christ, as though God did beseech you by us: we pray you in Christ's stead, be you reconciled to God.

1 Timothy 1:12 And I thank Christ Jesus our Lord, who has enabled me, for that he counted me faithful, putting me into the ministry;

2 Timothy 2:2 And the things that you have heard of me among many witnesses, the same commit you to faithful men...

faithful ambassador or an ambassador of faithfulness