Vivek Santhosh’s review published on Letterboxd:
Just like Badlapur, the thought process behind this movie was indeed noteworthy which tries to put the audience in a dilemma about which side to root for, by illustrating the uncertainties of the thin line between good and evil. But apart from the well-defined characters and the much needed intense mood which was maintained throughout, Padmakumar's lackluster making and Suresh Babu's screenplay that got partially lost in translation hardly succeeds in conveying that brilliant idea in a simple manner to a normal cine-goer who would naturally view it as just another revenge thriller, unlike Badlapur which managed to haunt most of the serious moviegoers for days.
Mohanlal was fine as usual while playing a role that sported heavy grade shades for the most part of the movie, but there's nothing extraordinary enough to challenge his prowess. Even the supporting cast has been just borderline decent. And it is also Padmakumar's lazy making that paves way for the audience to notice every single logical loophole in the narrative which are aplenty. The addition of unwanted songs, mediocre editing, long drawn out flashbacks and tasteless romance only helped in slackening the pace and lengthening its tiring running time close to 160 odd minutes. With a better director at the helm, this subject surely had immense potential with strong content for making a haunting experience.
On the whole, Kanal is definitely a watchable thriller despite its heavy logical flaws and outwearing running time that should have been foreshortened, for the intense mood it provides and the overall cerebration behind it. And yeah, there was hardly any kind of unwanted heroism, forced twists and conventional concepts etched out for a typical villain as a breath of fresh air.