Once you have completed:
Level 14 “Steppenwolf Surprise”
You will come across a few more new characters and varied abilities to use during this level, nothing too technical or confusing to worry about.
*** Spoiler - click to reveal ***Once you have gotten to the train and worked your way across defeating the 2 wolves, you will need to kill Stepponwolf with a few combats hits then finally putting him down with the Batman plane.
Then after a cinematic pop achievement unlocked.
Congratulations!
Happy Hunting