Game concept

Strong Vassal

The game also links it as Strong Vassals.

From the game's encyclopedia

A Strong Vassal is a Vassal who approaches or exceeds their Liege in power, incurring an Opinion penalty. They see their liege as weak and ill-suited to rule the realm.

The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.

Strong Vassal is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "A Strong Vassal is a Vassal who approaches or exceeds their Liege in power, incurring an Opinion penalty." It is part of Vassal. The game also links it as Strong Vassals. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.

for a guide, post or blog

Source: game/common/game_concepts/00_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.