Nephrotic Syndrome: The patient presents with bilateral pedal pitting edema, severe anemia (Hb 6.3), low albumin (2.09), and normal renal function tests. These findings are highly suggestive of nephrotic syndrome, which is characterized by heavy proteinuria, hypoalbuminemia, hyperlipidemia, and edema. The normal TLC, TPC, and RFT support this diagnosis, as nephrotic syndrome can present with relatively preserved renal function despite significant protein loss.

Hypothyroidism: Although the patient has high T3 and T4 levels with a normal TSH, which might initially seem to rule out hypothyroidism, the clinical presentation of severe anemia, edema, and underweight status could still suggest a thyroid disorder, particularly if there's a possibility of a pituitary or hypothalamic issue affecting TSH regulation or if the patient has a condition leading to elevated thyroid hormones without typical hyperthyroid symptoms (e.g., T4 and T3 toxicosis without thyrotoxicosis due to other systemic illnesses).
Chronic Liver Disease: Despite normal liver enzymes, the low albumin level could indicate liver dysfunction, as albumin synthesis is a key function of the liver. However, the absence of other liver enzyme abnormalities and the specific pattern of other findings make this less likely compared to nephrotic syndrome.
Malnutrition: The patient's underweight status and low albumin could suggest malnutrition, which can lead to edema and anemia. However, the severity of anemia and the presence of pitting edema are more suggestive of a systemic disease process like nephrotic syndrome.

Heart Failure: Although less likely given the patient's low blood pressure and the absence of other symptoms like orthopnea or paroxysmal nocturnal dyspnea, heart failure can cause bilateral edema and should not be missed due to its potential for severe morbidity and mortality. Echocardiography and further cardiac evaluation might be warranted.
Malignancy: Certain malignancies can cause nephrotic syndrome or severe anemia. A thorough investigation, including imaging and possibly a bone marrow biopsy, might be necessary to rule out an underlying malignancy.

Amyloidosis: This condition can cause nephrotic syndrome and severe anemia. It's less common but should be considered if other diagnoses are ruled out, especially with persistent and unexplained symptoms.
Systemic Lupus Erythematosus (SLE): SLE can cause nephrotic syndrome, anemia, and a variety of other systemic symptoms. Although less likely given the information provided, it remains a consideration in the differential diagnosis of a patient with multi-system findings.