Before you leave after raising your eyebrows, do give me a chance and test out this build yourself.
This is a cheap build for [Mag] with less focus on survivability but i assure you that it can clear any room on any level.

I'll start off by explaining the usage of her 4 abilities:
1)Pull - due to the low strength, this skill will not pull the enemy instead it will cause the enemy to fall down while moved only a little. As this is cheap, has enormous range, and will not interrupt any action, this skill is a very good crowd control. Personally will suggest you to spam this skill as often as possible in this build.

2)Magnetize - the star and focus of this build. As you guys might be wondering what can [Mag] do with negative strength? check out this clip below
(please forgive me for the bad quality)

Not amazed? what about this next clip

I DARE CHALLENGE ANY FRAME TO KILL 8 BURSA AS FAST AS [Mag]

Magnetize not only can kill the target inside the bubble, it will also deal explosion damage outside the bubble potentially killing the whole room of enemy with a single spell. The reason of going max range is so that detonating the bubble will kill as much enemy as possible and not just killing the main target

As magnetize explosion cannot go through walls and body, simulacrum is not the best place to demonstrate her power thus some grineers survived

The bubble can also be abused as it provides a protective barrier allowing safe reload or casting ability 4.

3)polarize - unfortunately for this build, polarize remove too little armor/shield and provide too little shield for ally. Therefore this ability is useless in this build.

4)Crush - This ability is used to replenish shield as well as providing over-shield for the whole team. Due to the fact that this casting this ability require to stand still, it is advisable to use pull for CC and cast crush when taking [Shelter] inside magnetize bubble.

Due to the sheer power of magnetize explosion, it can literally burst through even armor or shield of any enemy of lvl 110 or even higher, rendering armor removal obsolete.

For those patients fellas who read my guide and actually tested it, congrats on you guys as I believe this build is more optimum at killing rooms of high level enemy compare to strength [Mag] that focus on armor removal.

If you like this build, make sure to upvote so this will be the next meta for [Mag].