Leadership effectiveness can be measured at the individual and collective level. There are several measurements in the field of leadership adopted by top scholars.
To measure leadership effectiveness at the individual level, I would suggest items from the Multifactor Leadership Questionnaire developed by Bass and Avolio (2000).
To measure leadership effectiveness at the collective level, I would suggest items from these studies: Schaubroeck, Lam and Cha (2007); Tsui, Pearce, Porter, and Tripoli (1997); and De Dreu (2007).
The question you propose is complex and diverse because the objectives and corporate culture of each company are different and the measurement and homogenization of qualitative management aspects is always complex. However, I can recommend two tools that serve to measure the organizational leadership capacity.
1.- The EPDQ 4-Executive Position Description Questionnaire is a questionnaire that allows evaluating current training needs at the level of tasks and people. It allows describing the areas of work and the demands of different management positions, to draw the profile of a management position through ten dimensions. It also offers the possibility of assessing in a standardized way the work done by people in management positions. It also allows analyzing tasks and people, their behavioural nature when performing them, and detecting current needs.
2.- The LBDQ XII (Leader Behavior Description Questionnaire) seeks to determine the types of behaviours of leaders.
This instrument consists of 12 factors that identify and value behavioural differences of leaders in different organizational cultures. Their results serve to dictate guidelines and content of leadership development programs.
I am looking specifically at an individual level. I have narrowed it down to Kouzes and Posner (1998) Leadership Practices Inventory (LPI) individual measurement instrument and the Multi-factor Leadership Questionnaire (MLQ) . The variables being considered are sustainable practices, leader capacity, training and culture.
As an FYI this will be done online given the number of participants. I will review the instruments and guidance posted.