You can set up User Segments for each of the different cohorts. Create a custom segment, and add a Condition for Event Label exactly matches the event you want to see achieved. If your events are sequential and mandate the prior event to occur, you can create a series of segments to build your funnel. An example:
- Segment 1: All users (100%)
- Segment 2: Completed Event A (86%)
- Segment 3: Completed Event B (27%)
Once this is completed, return to Audience > Overview, and show the number of users. Voila.
If you want a traditional cohort graph (where the sum of the cohorts is 100% and you're just looking at relative sizes), you'll need to export the data into something other than Google Analytics.
The main limitation of this is that it's for all users. If you're asking the arguably more valuable question of cohort performance for new users (i.e. removing the skew of existing users/"survivors" making your site/app look better than it is), then you need to set up a segment for each cohort for each date range. Quite a pain, even if you're just doing monthly!