The first boss of this spiritual successor to the 2D Castlevania games is a decent one, you obviously face it during the end of the last level.
Being based on old school trains, it mainly tries shooting flames at you. Which are easy enough to avoid.
Doesn't take much to finish it off. It will throw some platforms at you which you can use to get some direct easy hits in.
Like almost every boss of the game, the train tries to take you to the grave with it in one last final attack. I will say I never saw that coming.