One way i could see this going down
superman and adam are on there way to confront the runner, the runner has been spotted charging towards them by supes due to super speed vision(what ever) as he tells adam to brace himself adam disapears asif its a poof of smoke,the runner and adam are poofing all over the place adam is then launched at supes but clark dodges him, adam is bloodied and unconsious, he turns back to the runner who is no were to be seen, clark then realizes he cannot stop smiling even though he is angry, then in literally lquicker than a blink superman gets upper cutted into earths higher atmosphere, the runner squares of with supes, then after a little scuffle the runner using his cosmic awareness and primordial powers senses the increasing solar radiation coming from clarks body, he then puts two am two together and realizes superman gains power from absorbing radiation from the yellow star, using his vast almost instant speed he transports him an supes to different regions of the universe in front of different stars, after a 10 minute fighting session, come across a red star, superman becomes astronomically weaker and runner begins to toy with him, then out of no were somehow adam had found them, he sucker punches runner who applauds adam on his efforts to save his friend, adam is then pasted and launched into the red sun, the runner can feel supermans heart and spirit, pulling through against all odds, he smirks at superman and tells him he loves a challenge, using his vast molecular manipulation powers he gives his cape the mass/density of a large planet, with adam dead and superman almost slug like to the runner, he realizes supermans tremendous strength, heart an spirtit will not be broken, he goes at clark with every ounce of power hes got for one final blow, enhancing his speed and strength beyond measure using his control over the power primordial, implants his fist into clarks face, causing shockwaves and ripples through out the milky way, supermans limp body drifted away, and a blurred line of fine gold vanished.
thats just being generous, the runner would of ended them in the first paragraph