From working together to both want the other to get killed. From closest allies they became the worst ememies, even though Jesse betrayed Walter to Hank and DEA Walter still saves him on the last Breaking Bad episode and Jesse refuses to kill Walter. I never understood their complicated relationship, at first Jesse does not betray Walt to Hank, at next Walt saves him from the drug dealers that killed a child-soldier, also Jesse killes Gale in case of Walt not get killed and finally Jesse doesn't let Gus to kill Walt. Why they saved each other lifes and at next Jesse betrayes and wanted to kill Walter after he saved him from the police and from death and Walter was also wanting Jesse dead after he saved his life by the dealers