"Everything That"
To say "all that" or "everything that," you can use the relative pronoun cuanto or the phrase todo cuanto. In this context, it means the exact same thing as todo lo que.
| An altruistic person shares everything they have with their fellow human beings. | Una persona altruista comparte todo cuanto tiene con el prójimo. |
Like other relative pronouns, the mood of the verb following cuanto depends on how certain or specific you are. If you are referring to known, established facts, use the indicative.
| The selfless effort demonstrates all that we achieve with kindness. | El esfuerzo desinteresado demuestra todo cuanto logramos con la bondad. |
However, if the exact amount or thing is unknown, hypothetical, or yet to happen in the future, you must use the subjunctive.
| I hope we are supportive and contribute with all that we can. | Ojalá seamos solidarios y contribuyamos con todo cuanto podamos. |
"All Those Who"
When referring to people rather than abstract things, cuanto must agree in gender and number (cuantos, cuantas). In these cases, it means "all those who" or "as many as."
| The shelter protected all those who arrived yesterday. | El asilo amparó a cuantos llegaron ayer. |
The same mood rules apply here: use the indicative for specific people you already know about, and the subjunctive for unknown, future, or hypothetical people.
| Feeling empathy for our fellow human beings, we will help all those who suffer. | Sintiendo empatía por el prójimo, ayudaremos a cuantos sufran. |
In the Past
You will also frequently see todo cuanto and cuantos paired with the past subjunctive when expressing past expectations, desires, or hypothetical situations.
| We hoped you would support the cause with everything you had. | Esperábamos que apoyaras la causa con todo cuanto tuvieras. |