We have already considered the case of those who scored a century on Test debut and never again:
Here we look at the cases of those who scored 50+ on debut and never again.
There are 117 players who scored 123 scores of 50+ on debut-see the list below.
The only double century here is by DSBP Kuruppu, and there are several other centuries.
Also note the cases of those who scored 50+ in both innings, but never again.