The punishment that I would advocate would vary greatly depending on the circumstances.
The main thing that I would need to know is whether the executive should have known that the product was potentially lethal. It is possible that the firm would have developed a product, tested it extensively and responsibly, and yet somehow simply missed a way in which the product could be lethal. In such a case, it would be hard to punish the executive in any way since that person did everything within reason to determine if the product was safe. The firm would surely need to compensate victims, but no punishment of the executive (legally speaking) would be warranted.
This would be different if the executive could have known by making a reasonable effort. For example, if there were tests that could have been run, but weren’t, I would want to punish the executive more. In such a case, perhaps a stiff fine and a short prison term would be in order.
Finally, if the executive willfully refused to know, I would punish that person much more harshly. In other words, if the executive said “I don’t want to be told if there is anything wrong with this product,” they should be punished rather harshly. Perhaps a very large fine and a medium prison term would be appropriate.