Do Christians believe that more sinful people suffer more on Earth? I wonder what Christian groups believe that more sinful people suffer more on Earth due to God's punishment?
As a note: I am non-denominational (just a Christian).

I think there is a difference between Israel and the other nations. Other nations did not make an oath in which they agreed to be cursed if they did not keep all the commandments of the Torah (Lev. 26:14). However, Israel did (Deut. 27:26). 

As for humanity in general, Jesus said (Matt. 5:45), "That you may be the children of your Father who is in heaven, for He makes His sun to rise on the evil and on the good, and He sends rain on the righteous and on the unrighteous."

There are some terrible things that happen to pious Christians, and sometimes generally "bad" people get through life "unscathed." I don't necessarily believe that bad people suffer more on Earth than Christians. But, at the last day, there will certainly be a different fate for each.