、。
What I regret now is, rather, the time I wasted.
Literal
Now regret-[progressive-ている] thing [topic-は], time [of-の] waste [object-を] did thing [the side of-のほう] [copula-です].
The sentence uses a nominalized こと clause ('the thing that I am regretting') as the topic, then equates it with another こと-nominalized phrase ('the thing of having wasted time') plus のほう 'the side of.' のほう typically marks one option in an implicit comparison; here it subtly frames 'time wasted' as the regret that outweighs others. The structure is heavy on nominalization, typical of reflective written Japanese.