Strong distortions is generally observed in high spin d4 , low spin d7 and d9 configurations in the octahedral environment. Reason: It is because the Jahn Teller distortion is generally significant for the asymmetrically occupied eg orbitals because they are directed towards the ligands and the energy gain is very high.
Jahn Teller distortion is very weak in unevenlly occupied t2g orbital beacause the t2g set does not point directly toward the ligands and therefore the energy gain is very less.
E.g. d1; d2; low spin d4 and d5; high spin d7 and d7 configurations.
Electronic configuration of central metal atom in the provided complex is given below:
Ti +3 = 3d1
Cr+2 = 3d4
Fe+2 = 3d6
Co+2 = 3d7
So, the complex which show strong distortion is [Co(H2O)6]+2