Let me start by saying the the H3 Spike Grenade (SG) is very different from the Infinite version. But their roles are the same. It is a grenade that allows you to control the direction of its explosion. I think Infinite does it better though.
Damage
The Infinite SG doesn’t kill at point blank, but frankly, that doesn’t determine a grenade’s worth. Frags and Dynamos also don’t kill with a single nade at point blank. The only nades in Halo’s history that have are:
- Stickies
- Firebombs (OP af)
- H3 Spike Grenade (as we’ve both observed. They’re inconsistent, I’ll get to that)
- Pulse Grenades (damage over time, unreliable)
- Splinter Grenade (probably the strongest nade).
Purpose
The idea behind the SG is that it’s supposed to do indirect damage by sticking to opposite walls and ceilings. They are highly influenced by map geometry. Basically this means that they should never be orientated in a way that the spikes shoot upwards (unless there is a low ceiling). I don’t know what your proficiency is with SGs, but if you’re throwing them at the ground, that’s where you’re messing up.
As for why the H3 SG kills in one blast, that has to do with how it detonates. H3’s comes out in a pretty tight cone, so if you are close enough to the direction of the explosion, you die. But because of this tight cone, the H3 SG has a very small splash radius. So small that grenade either does all or very little damage to no damage. Rarely does it do in-between.
The Infinite SG has one of the largest explosion radiuses. I’ve even hit people around distant corners (which is kind of the point of grenades). This is due to the fact that the spikes are much more likely to bounce back and home in the the target(s). The H3 SG does bounce around, but the spikes are prone to embedding themselves in the terrain. A notable exception is when the spike are trapped inside a bubble shield. The shield is energy so the spikes bounce around for much longer and eventually kill whatever is inside.
Also I’m almost certain the “homing” on the spikes is designed to ignore friendlies and yourself. So if you’re just throwing your own grenade at your feet, you might want to have a friend try throwing it instead.
This larger slash radius makes the SG ideal for clearing out rooms. If you think someone is hiding in a room (happens a lot on Bazaar, conveniently has 2 SG spawn pads), throw a spike grenade in there rather than a frag. It would also do very well on Recharge I think.
Conclusion
All of this said, I do think the Spike Grenade is the weakest of the bunch in Halo Infinite. So much so it is always the one I drop when I have the choice to get a different type (especially in BTB. Never use these in BTB). Its usefulness is amplified by the environment, but that’s also its downfall. It’s situational.
TL;DR: It’s basically the grenade version of the Heatwave.
TL;DR 2: Just stick them.