Here's my brief Catholic response to the Good Thief "trump-card" some Protestants use, and which I turned into a cut-n-paste response since I encounter it often enough:
The “Good Thief” (Lk 23:39-43) is often cited as the star
example of getting saved by faith alone. But here’s why the mature Christian
wouldn’t say that: (1) We don’t know his faith background, e.g., if he was ever
baptized in the past or if this was his first time meeting Jesus. His prayer “Jesus
remember me when you come into your kingdom” shows he had some knowledge of the
Gospel, since no such “kingdom” details are given in this passage. (2) Terms
such as ‘faith’ and ‘belief’ are not used in this passage, so there’s no reason
to think ‘faith alone’ is even the focus, just as the Parable of the Pharisee
& Tax Collector (Lk 18:9-14) doesn’t use such terms, but rather highlights
the virtue of “humility”. In fact, we see a range of virtues being expressed
here, including ‘Fear of the Lord’ (23:40; cf Prov 1:7), Repentance (which
Jesus distinguishes from belief, see Mark 1:5), Warning Sinners (2 Thess
3:14b), Public Professing (John 10:42; Rom 10:10b), as well as Hope of going to
Heaven and certainly Love for Jesus. The thief was even willing to suffer and
die for his own sins, not to be freed from them, which means he carried his own
cross (Lk 9:23). So this was *far from* faith alone. (3) This was a unique
situation, it isn’t the norm for how people typically accept the Gospel (see
Acts for the norm), and as such it has its limits. For example, Jesus had not
yet Resurrected, Ascended, or sent the Holy Spirit yet, so Dismas probably didn’t
profess faith in these, whereas these aspects of Jesus’ mission are required
for us to profess (Rom 10:9b). Even the command to “baptize all nations” wasn’t
even given until *after* Jesus resurrected (Matt 28:19), so pointing to this as
an example of ‘not needing baptism’ is kind of moot. Plus, can we take this one
example as an excuse to ‘not really have to’ obey the many teachings of Jesus
and the Apostles, including getting baptized, gathering to worship with others,
being subject to your pastor, sharing our possessions, etc? (4) Lastly,
Catholics highly honor the Good Thief, Saint Dismas, on March 25 every year,
and many Catholic Saints have preached on his beautiful testimony for us. So it’s
not like St Dismas (whom we have the decency to call by his actual name) is some surprise that theologians have missed all this time.
For example, St Augustine preached on how this is the only death-bed repentance
in the Bible, teaching us that while there’s always hope, we also shouldn’t be
too presumptuous about waiting until the last minute to repent. And some saints
have preached that the thief was partially converted by the prayers and
testimony of Mary and the holy women and John, standing at the foot of the
Cross praying for both criminals, showing us that we have a role in helping
others come to Christ.
UPDATE 5/4/22 - I would add that many Protestants think that Dismas went immediately to heaven, but the reality is heaven was not open yet until after Jesus was Resurrected and Ascended, which means Dismas went to Hades/Purgatory when he died, and Jesus only came down a few hours later when Jesus died. This is the "today you will be with me in Paradise" and what Acts 2:27-31 shows, that Jesus died and went to Hades. So Dismas was at minimum in Hades and possibly suffered some temporary Purgatory if Dismas's crucifixion suffering didn't do sufficient penance.