What would Christianity be like with the contribution of St Paul?

Presumably: exactly as it now is.

It would not exist, as he made most of it up himself. It is often referred to as Pauline Christianity.

Paul is a "saint" only in the sense that ALL who are of The Body of The True Church are Saints...... the man-invented titles of the papist catholics have been given without any authority from The Creator God ..... and are not taken into account by God in determining who will enter Heaven...... in fact.... it is likely that most of the so-called saints named by the papists will not be found in Heaven................. Paul was the Last Apostle approved by God... he was chosen by Jesus, and commissioned by God, to go out to the Gentiles and give them The Good News........ it was not until the ministry of Paul that the title of Christian was applied to those of God's Church

Paul created Christianity when he could find no other way to stop the movement Yeshua actually founded.

It it wasnt for Paul of Tarsus Christianity would likely be some quaint and relatively unknown religion in the middle east like the Druze or Yazidis.

I'm not going to make assumptions except that you mean without Paul's contributions. If you look at Paul's contributions he put in significant writings to the churches and work with the apostles, elaborating on advanced doctrines and setting records straight to clear up any lingering ambiguities.

I guess You mean "Without".

Christianity would always be the same. If it werent st paul it would be another person. God will always find someone to spread his words.

What would your question be like if you bothered to proofread before posting?

Christianity already has it.

With? Or without?

Nonexistent.