だけは

The structure だけは is used to emphasize that one does at least something, or does something to the fullest extent possible. It highlights that while other things may not be achievable or guaranteed, the speaker ensures that this one thing is done properly or completely.

Doing at least the minimum

When combined with verbs, だけは can express the idea of doing at least a particular action, even if one cannot do more. It carries the nuance of "at the very least" or "if nothing else."

Doing as much as one can

When the same verb is repeated in the pattern V（る）だけは V（た）, it emphasizes that the action was done to the fullest extent possible, though the outcome or result may be uncertain or unsatisfactory. This pattern often implies "I did everything I could."

Emphasizing a particular quality or exception

だけは can also single out one particular item or quality for emphasis, meaning "at least this one thing" stands out or holds true, even if other things do not.

Nuance

だけは differs from plain だけ ("only") by adding the topic/contrast particle は. This creates a sense of singling out or contrasting the item marked with だけは against other possibilities. It often carries a tone of "even if everything else fails, at least this much..."