Kura Ookami wrote: First how important is fellowship? God commands us to lean only on Him, "Love the LORD God with all your heart, all your mind and all your soul. This is the first and greatest commandment." So are christians supposed to join other christians in fellowship or to go it alone with Gods perfect help?
Second, how do we as christians treat those who would do us harm? Jesus commands us to "Do unto others as we would have them do unto us." So if someone treats us with cruelty what is the best thing for us to do in response to those people?
Indeed, God's help is perfect. And if you are perfect in accepting that help, then all is good and well and the need for fellowship with others is reduced. Although, being social creatures, even the most hermit-like people need fellowship from time to time.
Even if you are perfect in your acceptance of help, know that not all people are such. And those who are not perfect in their acceptance need the fellowship of others to help them accept what is truly of God. So, once again the need for fellowship arises. Or can you be so perfect that you do not need to help others?
Kura Ookami wrote:Second, how do we as christians treat those who would do us harm? Jesus commands us to "Do unto others as we would have them do unto us." So if someone treats us with cruelty what is the best thing for us to do in response to those people?
You have answered your question in your own question. Please note Christ said, "Do unto others as we would have them do unto us" and not, "Do unto others as they have done unto us."
Romans 12:19-21
"Beloved, never avenge yourselves, but leave room for the wrath of God; for it is written, "Vengeance is mine, I will repay, says the Lord." No, "if your enemies are hungry, feed them; if they are thirsty, give them something to drink; for by doing this you will heap burning coals on their heads." Do not be overcome by evil, but overcome evil with good." (NRSV)