Nothing wrong with the other solution, but it tries to go for the secondary objective which is to damage the terminator as much as possible before killing him. For the purpose of the achievement, we just need to kill him, so it's waste of time to damage. Here's my take on this going straight for the jugular.
To unlock this level, you do need to have completed the first 50 levels and have more than 250 stars. Now, just move the two blockades that are all the way on the right side to the top near the bolts, so the guy walking upwards doesn't walk straight toward the terminator. Now, place one bolt in the bottom bolt shooter thing. Sabotage the liquid nitrogen that's a bit above and to the left of that. There is another blockade near where you started the level, move that to where the oil puddle is so that peds are not walking toward the terminator when he enters that area. After that, use all 3 blockades to clear the bottom street area by blocking any peds that try to walk that way. Peds sometimes move slightly differently, so it may or may not always go the same way, but you should be all good after couple tries. Once terminator is hit with liquid nitrogen and completely stopped, shoot him, and you are done.
That big huge block of text is probably too hard to read and understand, so tl;dr, watch the video:
You are terminated! Hasta la vista, baby!