Which words and phrases in the text tells us that the convict is a wretched man?

In the early chapters of the novel, the young Pip has a dramatic meeting in the marshy fens with the escaped convict Magwitch. Pip's vivid description of the man tells us that the convict is in multiple ways wretched or miserable. We learn, for example, that he is out in the elements "hatless" and that his shoes are "broken." He is a man who has "been soaked in water, and smothered in mud," meaning he has spent some time already hiding in the marshes and so is very wet and dirty. He has been

lamed by stones, and cut by flints, and stung by nettles, and torn by briars; who limped, and shivered, and glared and growled; and whose teeth chattered in his head as he seized me by the chin.

In other words, escaping over rocks in broken shoes has cut up his feet so badly that he is limping. We learn that he is very cold, for he "shivered" and his "teeth chattered." Pip notes too that

he hugged his shuddering body in both his arms —clasping himself, as if to hold himself together—and limped towards the low church wall.

Magwitch is clearly doing very poorly.
Later, when Pip comes back to Magwitch with food and file, he again notices that the man is cold and also extremely hungry:

He was awfully cold, to be sure. I half expected to see him drop down before my face and die of deadly cold. His eyes looked so awfully hungry, too, that when I handed him the file and he laid it down on the grass, it occurred to me he would have tried to eat it, if he had not seen my bundle.

Magwitch himself speaks of what a desperate condition of wretchedness he is in. He calls himself a "wretched warmint, hunted as near death." We learn that he is psychologically at his end too, feeling very sad and alone. He fights back tears:

And he smeared his ragged rough sleeve over his eyes.

What we experience in these opening chapters is the description of Magwitch as understood by a young boy. As readers, we can figure out that a man in as bad a shape as Magwitch can't pose much of a threat, but Pip is too young to know this, and the convict is able to frighten him. Dickens's repeated descriptions of his wretchedness and desolation, however, help build reader sympathy for this convict.