I feel like Ryo doesn't realistically stand a chance against Lan Di in a one-on-one fight so revenge is out.
Why didn't Ryo simply sue Lan Di for the wrongful death of Iwao?
Ryo could have easily demonstrated Lan Di was liable for Iwao's death and the Chi You Men had very deep pockets so he could have gotten a huge Jury award or settled with the cartel for big bucks and been set for life.