You vastly overestimate the need for soap to be insanely powerful.
Who said anything about powerful? The powerful soap I mentioned was a bar soap and yet I clearly said liquid soap is preferable in everyday situations. But while we're on the subject of powerful, that Dr. Bronner's castile soap mentioned above comes in a quart container for $15, can be watered down to 1/50th its original concentration and still be useful and should last you approximately until the sun's expansion as a red giant makes soap unnecessary. Good luck watering down a bar of soap to make it last longer. Advantage: liquid soap.
As for convenience, liquid soap is self-contained in a bottle that can either be rinsed and reused or recycled when done; bar soap sits in a tray that gets scummy almost immediately because there is no way to use bar soap without picking up the entire thing, lathering it up and putting it back down with lather still on it, which then drips down into the tray and inconceivably turns it into a filthy, slimy, disgusting mess. The inside of a liquid soap dispenser is the cleanest surface in the known universe; the resting place of bar soap is a puddle of scum. How effective could it possibly be at cleaning if it turns its own home into a substance that if you stepped in, you'd throw out your shoes rather than attempt to clean them? Advantage: liquid soap.
Now, admittedly, once you get down to the end of a bottle of liquid soap and the pump no longer reaches into the liquid to extract more than a couple bubbles worth, the soap dispenser becomes an inconvenience. But when you get down to the end of a bar of soap, it starts splintering and coming off in weird semi-solid chunks that you realize are just coagulated scum. So you're either left pounding an upended bottle or picking perfumed shards of alkali smegma out of your fingernails; neither is preferable, but I'm going with the one that actually ends with me feeling clean. Advantage: liquid soap.