SQL Server 2019

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CREATE TABLE T1 (ID INT NOT NULL PRIMARY KEY);
CREATE TABLE T2 (ID INT NOT NULL PRIMARY KEY, FK INT NOT NULL, FOREIGN KEY (FK) REFERENCES T1 (ID) ON DELETE CASCADE);
CREATE TABLE T3 (ID INT NOT NULL PRIMARY KEY, FK INT NOT NULL, FOREIGN KEY (FK) REFERENCES T2 (ID) ON DELETE CASCADE);
CREATE TABLE T4 (ID INT NOT NULL PRIMARY KEY, FK INT NOT NULL, FOREIGN KEY (FK) REFERENCES T3 (ID) ON DELETE CASCADE);
CREATE TABLE T5 (ID INT NOT NULL PRIMARY KEY, FK INT NOT NULL, FOREIGN KEY (FK) REFERENCES T4 (ID) ON DELETE CASCADE);
CREATE TABLE T2A (ID INT NOT NULL PRIMARY KEY, FK INT NOT NULL, FOREIGN KEY (FK) REFERENCES T1 (ID) ON DELETE CASCADE);
CREATE TABLE T3A (ID INT NOT NULL PRIMARY KEY, FK INT NOT NULL, FOREIGN KEY (FK) REFERENCES T2A (ID) ON DELETE CASCADE);
CREATE TABLE T3B (ID INT NOT NULL PRIMARY KEY, FK INT NOT NULL, FOREIGN KEY (FK) REFERENCES T2A (ID) ON DELETE CASCADE);
CREATE TABLE T4B (ID INT NOT NULL PRIMARY KEY, FK INT NOT NULL, FOREIGN KEY (FK) REFERENCES T3B (ID) ON DELETE CASCADE);

WITH OnDelete AS
(	SELECT f.parent_object_id,
			f.referenced_object_id,
			RecursionLevel = 1,
			ObjectTree = CONVERT(VARCHAR(MAX), CONCAT(OBJECT_NAME(f.parent_object_id), ' --> ', OBJECT_NAME(f.referenced_object_id)))
	FROM sys.foreign_keys AS f
	WHERE f.delete_referential_action_desc = 'CASCADE'
	UNION ALL
	SELECT	od.parent_object_id,
			f.referenced_object_id,
			od.RecursionLevel + 1,
			ObjectTree = CONVERT(VARCHAR(MAX), CONCAT(od.ObjectTree, ' --> ', OBJECT_NAME(f.referenced_object_id)))
	FROM	OnDelete AS od
			INNER JOIN sys.foreign_keys AS f
				ON f.parent_object_id = od.referenced_object_id
				AND f.delete_referential_action_desc = 'CASCADE'

)
SELECT	BaseTable = OBJECT_NAME(od.parent_object_id),
		OnDelete = od.ObjectTree
FROM	OnDelete AS od
WHERE	NOT EXISTS
		(	SELECT	1
			FROM	OnDelete AS ex
			WHERE	ex.parent_object_id = od.parent_object_id
			AND		ex.ObjectTree LIKE CONCAT(od.ObjectTree, '%')
			AND		LEN(ex.ObjectTree) > LEN(od.ObjectTree)
		)
ORDER BY od.parent_object_id;

BaseTable	OnDelete
T2	T2 --> T1
T3	T3 --> T2 --> T1
T4	T4 --> T3 --> T2 --> T1
T5	T5 --> T4 --> T3 --> T2 --> T1
T2A	T2A --> T1
T3A	T3A --> T2A --> T1
T3B	T3B --> T2A --> T1
T4B	T4B --> T3B --> T2A --> T1