I, with a long knife in my hand, can only do one move

Experience the world: Blood Blockade Front (main world) - Problem children all come from another world (to be completed to be continued) - Game life: Zero (to be completed to be continued) - Black Bullets (to be completed) - Spell Return (to be completed) To be continued)——Assassination Classroom (Ended)
Cheng Rang is selected by the system to become a player, and he can continue to become stronger as long as he experiences experience in various worlds.
However, due to an inexplicable bug, I was unable to complete the last novice guidance task and was unable to graduate from the novice training ground.
All attempts to escape here were in vain. After experiencing despair and maddening boredom for a long time, Cheng Rang found that only the weapons in his hands could bring him warmth in the void world.
Until one day, the system successfully detected and fixed the BUG.
At this time, Cheng Rang walked out of the novice training ground and discovered that even if he only knew one move, he could become very strong as long as he practiced it countless times.
......
A man remains a boy until he dies. This is the story of a boy pursuing hope in various worlds.
"As long as you still want to take a step toward the light, the human soul has not declared defeat."