its a combination of luck and skill to kill the ACW at low level. sometimes the ACW will do stuff even the best players can't do much about.
1) You can kill him with frost bolt, it will just take alot. If you have a meat shield between him and you, then he cannot bolt you back. His bolt can insta kill you below about 150hp.
2) You can use a ball spell with 32 WI to ball him around a corner
3) if you have more hp, you can do the water orb rope a dope. Basically you stand there and get bolted, if he hits, you heal, if he doesn't, you cast a spell. It is alot of corruption, not as much as you'd think.