Not only Lakhan each and every character of begusarai 1 is written and executed by very well which is rare in ITV.
I usually FF the Chacha-Chachi portions. Can't stand the overacting. CJL makers should realize that you can't just depend on the leads' chemistry. The supporting characters have to be written well too. They should have an arc and motivation of their own. Begusarai scored well in that department. Each of Lakhan's cousin's had their own arc and ambition to be the king of Begusarai. Even the vamp and dadi had a backstory of their own.
Chachi's motive to murder Tara seems silly by contrast. At the same time her argument that Ananya is not getting a good rishta because all the grooms are comparing her to Tara makes sense.In the olden days of joint family, all the cousin sisters of marriageable age were usually asked not to come out when a groom came to see the girl.
Even Rounak's character is one-note. He could have been shown as a charming, affectionate yet weak character.