One of the features of parser games is that they can have a huge number of possible actions (many of which may be unknown to the player). Which game do you think has the largest number of unique verbs that do different things (i.e. not just largest number of synonyms)?
Checking the sources of my own works, I see that (beyond the standard actions implemented in Inform 7), we implemented 17 extra actions in Sub Rosa and a whopping 77 additional actions in Calm. However that’s mostly to do with inefficiency of the code in this earlier work. (The likes of “Mushroom Picking”, “Hiding from it inside” and “Jumping in” are defined as unique actions.)
One move games have an advantage here, as they don’t have to deal with state interaction. There are actions that might give the same single response regardless of context (like jumping on the spot), and actions which dynamically change the world state (like taking). In a one-move game, they’re all of the first kind.
I was going to say Mirror and Queen, which has 3000+ keywords, but those aren’t verbs and aren’t unique.
Games I could see having lots of actions (but could be wrong!)
-Hard puzzle 4 (lots of weird items and interactions)
-Blue Lacuna and Counterfeit Monkey (large game means variety of interactions which means a lot of custom verbs which individually are normal but combined are a lot (?))
-Flexible Survival, for same reasons and due to numerous activities not considered by the standard rulebook
-The Gostak surely has numerous actions defined which aren’t standard