conflict

[1]	clash , disagree , differ , be incompatible/at odds/at variance , be in opposition (to)
[2]	run afoul , infringe , contravene

[1]	fight , battle , combat , engagement , struggle , war , fray , fracas , affray , brawl , Donnybrook
[2]	dispute , argument , controversy , wrangle , contention , disagreement , altercation , feud , quarrel , row , squabble , tiff , (Colloq) spat
[3]	clash , antagonism , difference , opposition , disagreement , variance , discord
[4]	difference of opinion