Will generated tokens be progressively stronger when using Cathar's Crusade and Sorin, Grim Nemesis?
All 35 tokens enter the battlefield at the same time. All creatures you control, including the 35 tokens you just created, will get 35 +1/+1 counters.
As Sorin's ability resolves, you carry out its instructions; in this case, create 35 1/1 creature tokens.
Cathars' Crusade will be triggered 35 times:

603.2c An ability triggers only once each time its trigger event occurs. However, it can trigger repeatedly if one event contains multiple occurrences.

If it were to trigger only once, its trigger condition would have to be worded differently, for example as &quot;Whenever one or more creatures enter the battlefield, [..]&quot;. As it is, it triggers once for every single creature entering the battlefield.
All abilities that do trigger during the resolution of a spell or ability wait until that spell or ability is fully resolved before they enter the stack:

603.3. Once an ability has triggered, its controller puts it on the stack as an object that’s not a card the next time a player would receive priority.
116.3. Which player has priority is determined by the following rules:
116.3b The active player receives priority after a spell or ability (other than a mana ability) resolves.

The abilities created by Cathars' Crusade work on all creatures on the battlefield at the time they resolve, not when it is triggered or when it enters the stack. Assuming that no player takes further action, the 35 Cathars' Crusade triggers will resolve and give every creature you control, including the tokens, 35 +1/+1 counters each.