SEOUL, South Korea — Lee Kun-hee, the former chairman of Samsung who was convicted of corruption last August but pardoned by President Lee Myung-bak four months later to help a campaign for the 2018 Winter Olympics, returned to the helm of Samsung Electronics on Wednesday.

He was the latest and most prominent ex-convict who has retained top management of major conglomerates here. In announcing Mr. Lee’s surprise comeback, the Samsung Group said the chairman would bring to its electronics subsidiary, and to the conglomerate as a whole, badly needed leadership at a time when global businesses like Toyota were tottering.

The manner of Mr. Lee’s return — as disclosed by a senior vice president and top Samsung spokesman, Rhee In-yong — spoke volumes not only about the power of the taciturn chairman at Samsung but also about that of other “owner chairmen” like him at their own family-controlled conglomerates, known as chaebol.

“This only proves how unreasonable Samsung can be,” said Kim Sang-jo, an economist at Hansung University and executive director of Solidarity for Economic Reform, a civic group. “His return only makes Samsung more vulnerable to the kind of risk Toyota faces. It shows how distorted and how closed its decision-making is. It shows Samsung’s lack of a mechanism to deal with errors.”