This is the 10444th most frequent Russian word.
вероятного
"Probable" or "likely."
The word 'вероятного' in this sentence means 'probable' and is used as an adjective in the genitive case referring to 'развития событий' (course of events).
Это было наиболее вероятного развития событий.
This was the most probable course of events.
Here, 'вероятного' serves as an adjective modifying 'воздействия' (impact), again in the genitive case, referring to a probability of the event.
Мы обсуждаем возможность вероятного воздействия.
We are discussing the possibility of probable impact.
In this case, 'вероятного' modifies 'варианта' (option) and suggests that options have different levels of probability.