The God of the Old Testament seems a lot more cruel and unforgiving than the God of the New Testament.
The prophet, Daniel would disagree with you:
"
9To the Lord our God belong mercy and forgiveness, for we have rebelled against him
10and have not obeyed the voice of the Lord our God by walking in his laws, which he set before us by his servants the prophets." - Daniel 9:9-10
Even though Israel repeatedly broke God's laws and rebelled against Him, still, He forgave them.
The list of people in the OT whom God forgave in spite of their wickedness is too long to list here.
Certainly David, guilty of adultery, murder, lying, political and moral corruption recognized God's mercy in Psalm 51:
" Have mercy on me,
a O God,
according to your steadfast love;
according to your abundant mercy
blot out my transgressions.
2 Wash me thoroughly from my iniquity,
and cleanse me from my sin!
3 For I know my transgressions,
and my sin is ever before me.
4 Against you, you only, have I sinned
and done what is evil in your sight,
so that you may be justified in your words
and blameless in your judgment.
5 Behold, I was brought forth in iniquity,
and in sin did my mother conceive me.
6 Behold, you delight in truth in the inward being,
and you teach me wisdom in the secret heart.
7 Purge me with hyssop, and I shall be clean;
wash me, and I shall be whiter than snow.
8 Let me hear joy and gladness;
let the bones that you have broken rejoice.
9 Hide your face from my sins,
and blot out all my iniquities.
10 Create in me a clean heart, O God,
and renew a right
b spirit within me.
11 Cast me not away from your presence,
and take not your Holy Spirit from me.
12 Restore to me the joy of your salvation,
and uphold me with a willing spirit.
13 Then I will teach transgressors your ways,
and sinners will return to you.
14 Deliver me from bloodguiltiness, O God,
O God of my salvation,
and my tongue will sing aloud of your righteousness.
15 O Lord, open my lips,
and my mouth will declare your praise.
16 For you will not delight in sacrifice, or I would give it;
you will not be pleased with a burnt offering.
17 The sacrifices of God are a broken spirit;
a broken and contrite heart, O God, you will not despise.
18 Do good to Zion in your good pleasure;
build up the walls of Jerusalem;
19 then will you delight in right sacrifices,
in burnt offerings and whole burnt offerings;
then bulls will be offered on your altar." - Psalm 51:1-19
Does that really sound like a God who is unforgiving?
He seems to wipe out entire towns and populations without giving them a chance.
Could you please give us an example of a place or a people God wiped out without first sending a prophet to them to plead with them to repent?
Also, could you please name a place or a people God was not justified in wiping out?
Also, there seems to be constant references online to slavery, sexism, and racism in the Old Testament.
So how do those things make God bad? That something merely exists is not an indicator of guilt.
Why does God seem to completely change course between the two?
I can't find any evidence that He changes course at all. We see plenty of forgiveness and mercy in the Old Testament.
The only difference I can find is that in one, He deals with people corporately and in the other, He deals with them individually.