When it comes to hardcore techno, and style/genre like gabber, hardstyle, speedcore, new style hardcore, oldschool gabber, etc. the kick drum is the more important part of the production:

the kick drum has to be ridiculously strong, and/or distorted, mangled to death, strong solid fat devastating and incredible.

For me the best combo is drum synth or sample + distortion (and couple of other effects like compression, distortion, EQ, and more distortion).
But sometimes it’s nice to have a dedicated plugin ! Here we go with the freeware plugins :

1. Gabber Master! VST by John Merrik

direct dl : Gabber Master VST download!

Join 16,000+ others and grab Kick Machine, a kick drum and bass generator for modern music styles. This VST-synth is developed by infected sounds in cooperation with CPS / Noizefield and the Guru. When looking for the best drum VST, remember that it isn’t always about how pricey it is. Price does not dictate the ability to use, and quite honestly, some of the free drum VST plugins out there are actually fully capable of blowing their pricey cousins right out of the water with ease!

It’s a Windows-only VST, it seems it has been created with Synthmaker, and should work well in 32 bit VST hosts sequencers.
The GabberMaster VST is sample based with a nice variety of samples, and some parameters for destroying the sound.
Instant gabber hardcore breakcore speedcore terrorcore !

Kickdrum -Drum Synth Vst Plugin: Price: Free: A neat sample based kick drum player created by Thomas Weber of amvst.com. 1xADSR Sample Player Multimode Filter Saturator. Kick Machine Free Join 16,000+ others and grab Kick Machine, a kickdrum and bass generator for modern music styles. This VST-synth is developed by infected sounds in cooperation with CPS / Noizefield and the Guru-Project team. Native Instruments trK-01 £89. NI’s intriguing new Reaktor Player instrument is dedicated to. 32/64 BIT AU & VST & AAX. KICK is available in 32 & 64 Bit in both Audio Unit / VST and AAX. I've been messing with this synth for the past week now and I can already see this is going to be my go to plug in for kick drum creation. Super simple, yet super powerful. Sign up for free or log in to download the KICK. Analog Kick offers a set of 10 analog kick drum samples. Original handcrafted samples. True analog sound source. Lightweight / no-nonsense design. 100% royalty free. Mac OS X AU & VST 32/64-bit.

2. Bassdrum::Murda VST by Distocore

Distocore Bassdrum::Murdaaaaaa

Information and download : http://www.distocore.net/

Concept by I:GOR , this free plugin is more sophisticated and is a powerful drum synthesizer:
You have 3 oscillators with many waveforms to choose from, envelope sections for the pitch and the volume.
The audio signal goes to filter + distorsion + bit crusher + eq.
Now you can create powerful hardcore kick drums from scratch.

3. Hardcore Kicks Lite VST by the CoreStylerz

Information and download : http://www.thecorestylerz.net/vst/hardcore-kicks-vsti-2/hardcore-kicks-vsti-2-lite

This one lets you make some noise too.
It is “facebook-like-ware”, not really freeware, but it’s nice and deserves some supports.
some agressive ear-destroying presets show the potential of this hard kick generator.

4. Synth1 by Ichiro Toda !

Synth1 VST ! Redrum vst free.

Or any synth with at least one or two oscillator, a pitch envelope and some saturation / distorsion / filter / EQ effect.

– turn off all effects
– start with OSC2 (mix 100% to the right), choose the triangle waveform,
– activate the Modulation ENVelope for Osc2 : set Attack to zero and turn up the Decay and AMounT
that’s a basic kick drum
Now you can destroy it with the effect section :

Free Kick Drum Vst

– choose analogic distorsion (A.D) or DECImator.
– for more funkyness, you can also add a filter lowpass (or bandpass) + filter envelope, crank up the resonance to add screaming.
Or choose a square waveform instead of the triange.

now you can mix with a kick sample, layer it, resample, do anything you want

Only Synth1 audio examples :

https://blog.wavosaur.com/wp-content/uploads/2014/08/synth1-corekick.mp3
https://blog.wavosaur.com/wp-content/uploads/2014/08/synth1-kick.mp3
https://blog.wavosaur.com/wp-content/uploads/2014/08/synth1-brainwashkick.mp3
https://blog.wavosaur.com/wp-content/uploads/2014/08/synth1-badboyyy.mp3

Free Trap Synth Vst

5. Virtual KickLab XL by Angular Momentum

Kick Drum Synth Free Vst

it’s here : http://www.amvst.com/kicklab-xl

A kick dedicated free plugin for Windows, you can create bass drum from scratch.
It’s not as ferocious as the other plugins in this list, but it can do some solid kicks.
It’s more clean, the saturator and distortion aren’t dirty enough.
But you can produce nice kicks out of it.