The concept is fine: They're attack buffs that behave like mini-Techniques in that they're at their best the first time you use them, adding more options to Intermission combat so it is more engaging.
So why'd they fail?
- Deathblows need frequent Intermission combat scenes. The Deathblow rules assume Matches will be frequent, possibly having more than one per Episode, which couldn't be further from the truth for most games of BCG. What is worse is that, having a whole page of rules to themselves, they imply that's not the case and invite new players to burn their CPs on them.
- Intermission combat is too quick for them to matter. Matches are often decided by Turn two, so the core Deathblow mechanic (gets worse on repeated use) might as well not exist. Worse, many of them buff following attacks, debuff incoming attacks, or get better the longer the battle goes on. None of these effects are worth your CP in a game of rocket tag.
- They can't be used against Mecha. Even after inserting a bolded line of text in the Deathblows section saying they don't work against Mecha, I still get asked if they work against Mecha. The confusion is understandable though, because if someone spends a bijillion CP creating a combat PC, how come some of their abilities arbitrarily don't work on robots? It creates frustration and that's not a good thing.
- Deathblows are too weak. Every previous point could be forgiven if Deathblows were worth their cost in CP. The individual review entries will go more in detail, but this point here is the final nail in the coffin.
And now for their individual dissection...
This debuff inflicts a Disadvantage to all Tests for a Round. You know what's an even better debuff to give your enemies? The K.O'd status. Get another Advnantage to your attack and don't take this.
All Allies gain an Advantage to attacking the target for a Round. This can sometimes be better than a single Advantage to all of your attacks, but it is unlikely to happen more than once, if ever. Better than Called Shot, but still not worth it.
This one causes Disadvantages to Willpower Tests made to stay in the fight. That's an alright effect for 5 CP. I wish the others were this good.
Forbidden Secret Art
This doubles the Tension bonus for one attack. So, for 10 points you get to double the +1 bonus during the first Round, which is to say, you just paid 10 CP for half an Advantage. Bonus: If you did your job and ambushed the enemy, the Tension bonus is 0. Avoid this like the black plague.
This lets you target multiple Enemies per Test, assuming they're all in the same Zone. Easily the best of the 10-costers and it might just be worth taking if you expect a lot of Intermission combat.
Lets you ignore Disadvantages to your attack. The best way to counter Disadvantages is to get Advantages of your own, and even if you somehow don't have any more to buy, you should be spending your CP on more Fitness instead of this.
A round of focused playtesting would have been enough to catch and then fix all the problems with these, but there was always something more important to work on. There was virtually no feedback about them, so Deathblows were generally left alone to work on something else.
If I were to redo them, Deathblows would be General Traits applicable once per Match. Each Deathblow would also grant one or two Advantages to the Test and you'd need to be trained in a Skill in order to use them, like with Gumshoe. Even then, a few are totally unsalvageable and should just be deleted.
So that's Deathblows, they're this game's absolute nadir, and it can only get better from here. But before we get to Powers, the first section directly relevant to mecha combat, we still have one last set of Traits to look at.
Next: We wrap up the Intermission abilities of the book with Anomalies.