SPOILERS ALERT - how did HE become so good at fighting and destroying tons of his enemies?
For not being any type of (apparently) cop, Army man, CIA or FBI agent or even some trained hitman, and for failing to stop a robbery in his own home, how did he later become so damn PROFICIENT at killing and fighting tons of his enemies including seasoned Russian and otherwise Mafia hitmen and surviving himself, essentially turning himself into a hybrid of Liam Neeson from the "Taken" movies and "John Wick" with typical Van Damme and Steven Seagal type of action movie characteristics?
Where did he learn all those skills, where did he get the determination, how come at one point he was even able to effectively use a weapon to SAVE someone like an experienced surgeon on top of everything?
Cheers. And of course I did watch the movie and all that.