Well even as you beated him already, i'm a master in doding really, and i find ihm pretty easy to counter.
in the first rounds where he is teleporting. you just wait for him to do that,
as soon he has teleported near you he will reveal hes weak spots (the heart) shoot it and he will be knocked back
you can also shoot him on hes back, (know this that you know howm uch health he got left as the color of that thing on the back wll turn orange, and red when hes really low)
at the other stages where he stats to make clones, well the way to know the real one is
1) he will reveal hes heart again
2) he will show a purple haze or something from hes mouth (thats the real one)
when he starts to triple teleport and the 2 first clones comes,
te first 2 you just wait to pass, once he appears, he will appear from behind you, just make a quick turn and shoot him fast on the heart to knock him off again.
Now the tricky part, now hes really angry and will start rushing towards you instead,
but i find it easy aswell, the trick is to dodge him here, just when hes near you and will start hitting you have to be quick and dodge him, and make a quick turn to shoot him on the back, do this a few times until he starts to crounch, and he will be dead in no time.
Make sure that you are using shotguns for the first stages in teleporting etc, which makes it easy for you to hit him,
just use all your ammos.
and the very last fight which is harder, use a assault rifle to kill him fast from behind.
(i post this so that other players also knows how to beat him faster and easier)
otherwise when he starts to use triple teleport
u can use your stash to dodge him too,
once he starts and the 3rd appears to hit you open your stash and close it, and he wont hit you. ^_^