Warframe have a few different enemy factions, I will introduce you to the four “main” ones that you will constantly run into :)
Corpus – tons of shields(!)
Corpus are the high-tech enemies with tons of shields which means Puncture and Slash damage won’t be very effective at all. You will need something to bypass or be effective vs shields specifically.
Corpus are Weak against Impact damage AND Gas+Magnetic Elemental Combo
That is where Impact damage type weaponry comes in when facing corpus – this will will definitely give you an advantage.
If you also have modded your weapons for Elemental combo of Gas+Magnetic they will be extra super-effective vs this faction.
Grineer – Heavily Armored(!)
The Grineer’s are heavily armored enemies – Which means damage type such as Slash will have little to no effect on the more heavily armored units that can be found within the Grineer faction.
Grineer are Weak against Puncture damage AND Radiation+Viral OR Corrosive+Heat(or Blast) Elemental Combo
If your bring Puncture damage instead you will notice a significant improvement dealing damage to the more heavily armored units of the Grineer – Puncture shreds their armor! Coupled with Corrosive (melts armor) and Heat (or Blast) Elemental Combo – you will basically melt the Grineer enemies you face (hopefully) :P
OR you can try using Radiation+Viral. Some prefer this – the radiation causes confusion leading to the grineer having a chance of attacking each other which counts towards crowd control (cc) which might be useful in battle vs. higher-leveled enemies – and the Viral bypasses all manner of “external” defenses causing damage to be dealt Directly towards enemy health! (bypasses shields etc). Feel free to experiment to find your personal preference :D
Infested – Low-no armor flesh units
Infested are “squishy” (low/no armor – flesh) enemies which means they are very weak and left without the shields or armor that helps “defend” grineer and corpus.
Infested are Especially weak to Slash, Corrosive and Heat/Blast
If you want to truly melt the infested you face, try going up against them with Slash weapons which will be super effective, and also mod the weapons with Corrosive + Blast and you will be Golden!
If you for some reason don’t want Blast you can also try out Heat elemental damage – also quite effective :)
There is a in-game weapon called Stug which perfectly shows how Corrosive Elemental damage is especially effective vs. the infested – everything simply melts away xD Try it and you’ll see for yourself :)
Void – a Corrupted mix of Corpus, Grineer and infested units
Void is a corrupted mix between corpus, grineer and infested enemy units and many people suggest corrosive + cold elemental combo against this, I think it’s hard to pick a side, I just always take something with high general damage – but in theory void enemies will scale and thereby increase in armor where corrosive is good, and the amount of shields they get can be weakened with cold damage(!) – which supports what people claim is effective vs these enemy units :)